Island2Dweller

Eurostar prices are higher than they used to be because they now sell fewer seats. At peak times there are long queues for boarding (you do Schengen immigration at the St Pancras terminal before you get on the train). Eurostar are now only selling two thirds capacity on some trains because of the delays in getting passengers through the revised (Brexit) immigration process. With less seats to sell they have less need for heavy discounts. Your travel date is relatively near and if you want to do this, firm up your plan and buy tickets now - ticket prices will only get more expensive. If you're starting in Southampton, the least hassle route is the train from Southampton to Waterloo, then grab a taxi for the hop across to St Pancras. Finally, to add emphasis, "Chunnel" is a word only used in North America and it just causes confusion here. Use Eurostar (passenger trains) or Eurotunnel (Car shuttle trains)

What's done is done. BA are absolutely rigid that if you have two separate tickets (even if both with them), they will not check through. Small mercy for you, at least this summer the Barcelona services are using their main terminal (T5) - previously they have used T3 which would have required a train ride between terminals as well. One final thing to check. London has six airports and BA fly from three of them. Triple check that the add on flight really is from LHR and not (for example) LGW or LCY

Train will be simpler. You seem to have been unlucky. On this sort of route, ticker prices vary by time of day. If you do get off your cruise very early (on a weekday), your only option will be the (most expensive) "anytime" fare. If you can delay leaving Dover until after (approx) 0900, you have cheaper "off peak" options. Speak to the ticket clerk as the "groupsave" fare may also save money. If you do leave Dover early (and hence have to buy an anytime fare), only but to London. Buy the ticker for the second stage in London (by which time you will qualify for a cheaper fare). Fast trains from Dover arrive at St Pancras, which is side by side with Kings Cross. Trains to Cambridge leave from both stations. The fares are the same. If aren't sure which station the next departure is from, the station staff can quickly check.

I can't think of anywhere in the UK where you pay to use toilets, and even if you did they would take a card. The UK (and especially London) has moved very rapidly away from cash, some venues in London now do not accept cash at all.

Using Oyster in London. Entirely possible, it still works, it was considered revolutionary when it was introduced. But it is now considered "old tech" and most fares are paid by contactless bank card or phone pay. Re the comments about turning the card in at the end of your stay, you no longer get the £7 cost of oyster refunded, so it will cost you more than using card or phone. Do NOT buy the visitor oyster in advance which costs you a lot more in non-refundable fees and has less functionality. (But you'll see lots of slightly misleading adverts for visitor oyster, all geared around the seller making good margin out of you) If you really want an oyster, buy on arrival, really easy.

As mentioned above, Brighton is well out of the way. Fairly slow and expensive by car. However, if you really want to see it, it's very easy by train, and probably just as quck as by car. Elizabeth Line from Heathrow to Farringdon, change there for the Thameslink trains to Brighton. Next day, there are direct trains from Brighton to Southampton. If you want somewhere much more "en route" to Southampton then Chichester is a good suggestion.

Greenwich "The arrival times may vary depending on the tides in the river. " There's no 'may' about it. You can only arrive and depart on the full tide, so times to arrive/depart Greenwich are always dictated by the times of high tide. Due to wind on the day, the actual time of high tide may vary by up to an hour from the prediction - the pilot will always work with the actual tide on the day rather than the predicted times.

Tilbury. It would be unusual for Viking to use Tilbury - they generally come much closer into London and moor at Greenwich. Assuming it definitely is Tilbury. Trains depart from Fenchurch Street (which does NOT have a tube station, but is a very short / 5 minute walk from Tower Hill on the District Line. The easiest option is to take the train to Grays (one stop before Tilbury). There will be taxis waiting outside Grays station, whereas there will not be taxis waiting at Tilbury. The taxi journey from Grays is not any longer. You can pay the rail fare with a contactless bank card (tap in at start station, tap again at Grays), which means you don't waste time buying a paper ticket AND is cheaper than a paper ticket.

Dover. Cruise ships moor at the Western Dock. It's about two miles to the castle. You can walk - but as the castle is on top of the cliffs, it's a sharp uphill walk. Or walk into the town (half a mile to a mile - depending on how far down the quay you moor up) and get a bus up to the castle entrance (you can use a contactless bank card to pay, no need for cash). Or call a taxi and they'll happily take you

What day of the week are you arriving? There are branches of the major firms (such as Hertz) near the docks, but typically in the UK city centre branches close at lunchtime on Saturday and don't open again until Monday morning. Airport branches (such as at nearby Southampton airport) have much longer hours, and might be your only option if arriving on a Sunday. Expect to pay a one-way fee, perhaps £50. Small cars will usually have manual transmission, if you want an automatic you need to specifically reserve this.

"What is the benefit to taking transport to Waterloo vs Victoria? " The frequent and fast trains from Southamton go to Waterloo. There is also a once per hour train to Victoria but it goes a longer route and hence takes considerably longer.

If you buy on the day of travel at Southampton station, the single fare is £152 (via Reading) or £99 (via Salisbury) If you buy an "advance" ticket, these can be available from £40. Note that "advance" fares are like air fares, they are quota limited, once the cheapest fares are sold more expensive fares are offered. The "advance" tocket is valid for the booked train (and connections) ONLY and if you miss the booked train then you have to buy a new ticket. The "advance" fares are available from about 10 weeks ahead, though it's not an exact science and it may be a bit after that. The chief operator on that route is GWR - there are known issues with their web site and non-UK credit cards. If you hit a problem in trying to buy through GWE, use an alternative ticket site such as "ticketsplit". If you need to collect a physical ticket (and you probably will on a multi stage journey such as this), you'll need the physical card that you used to buy the ticket in order to collect it - so don't use a virtual card or phonepay

Getting an Uber to accept a drive of that time/distance is a bit of a gamble. I don't use Uber but I gather from friends who do (or rather, who try to) that drivers are much more picky about which jobs they accept. There is a shortage of drivers across the UK so the drivers have the upper hand.

The tidal range at Greenwich is up to 7 metres (about 23 feet). Ocean going vessels can only arrive / depart on a full tide, and as explained above the prediction is sometimes slightly adrift of the actual full water time.

We'll purchase Oyster Cards before we go Suggest you don't. Buying these and having them shipped costs far more than buying on arrival, and the visitor version has less features than the regular one that you buy on arrival. You can buy at any tube station, really easy. Your reluctance to use a bank card is noted but if it reassures you, using card or phone is now the dominate payment method. Oyster still works but it is now "old tech" and costs you an extra £7 that you don't need to pay if you just use a bank card.

BA have 13 A350-1000 in service, more to come. They are allocated to a specific set of destinations, but they are a pool across those destinations - they don't allocate any individual aircraft to just one route. The only exception was their A318 models (they only had two) which operated exclusively between LondonCity (LCY) and NewYor (JFK). But these have been withdrawn.

"We will be taking the train from Southampton to Paris after the cruise and our TA has advised we will need to make 2-3 transfers between Southampton and London" Not quite. The train from Southampton to London is direct and reasonably fast. But it arrives into Waterloo station whereas Eurostar departs from St Pancras station. The transfers only come into play if you choose to use the underground to get between stations - you may prefer to do that hop (about a mile and a bit) by taxi

"I was wondering if the London Pass that I can buy through Viator is a good way to see the city." Not value for most people. Many major attractions (museums etc) are free. Of the paid attractions, you would need to rush from venue to venue to get "value". And for the transport element, it's easier/cheaper to just use your contactless card or phone - you never actually hold a physical travel ticket

"The regular Oyster card costs £7, but if you cash in the balance you get the cost back" This is no longer true - rules have changed - you will not get that cost back if you try to cash it in. If you keep the card, after a year (but not before) the £7 converts to usable credit. Oyster was revolutionary when it was introduced two decades ago but it is now considered "old tech". It still works but the majority of fares in London are now paid by contactless card or phone. You can travel to more places around London using card/phone than you can with oyster.

Because of the coronation, vast areas of central London will be closed to ordinary traffic on 6 May, and may not have fully reopened by the following day. So I'm not convinved a car service is your friend here. Depending on which hotel you are booked in, using train or tube is likely to be quicker, get you access to more areas, and vastly cheaper. Which train or tube option depends on which hotel you are starting from

Shuttles are almost unheard of in London. The public transport options are so extensive that there isn't a business model there

Rail fare from Kings Cross to Grays. The adult fare is £9.10 in peak time (Monday to Friday from 0630 to 0930 and from 1600 to 1900.). At any other time the off peak fare is £8.10 The simple journey is an eastbound Hammersmith line train to West Ham, then the C2C train to Grays. Just one easy change. There are lifts at these stations so not arduous with luggage. This is simpler and cheaper (and probably just as quick) as trying to get across the City in a cab to Fenchurch Street. The Hammersmith line trains are "normal" size (not small tube size) and are air conditioned. Using Grays (not Tilbury) is recommended because there will be taxis outside the station. Tilbury station is closer “as the crow flies” but because the taxi has to backtrack to get over the rail lines, it is (in practice) easier from Grays. Note. This is the fare using a contactless bank card or phone to open the platform gates (and not buy a paper ticket at all). Buying a paper ticket is possible but will cost much more.

Heathrow Express may be a good option if you choose a hotel right beside Paddington station. But if your hotel is elsewhere (and as Paddington is on the edge of central London, I'd suggest you want to be elsewhere) then it isn't your best choice. Choose the hotel first then ask for advice on how to get there. The new Elizabeth line (very comfortable, fully airconditioned) will get you to many locations in central London directly from Heathrow

In normal times, taking the Avanti train service from Edinburgh to Birmingham then an onwards connection to Southampton is a great option. But...... For the last few months the Avanti service has been little short of a disaster. Endless cancellations, and the route from Edinburgh is especially badly hit. This is because the management have failed to manage recruitment and simply don't have enought crew to operate the schedule. One would hope that by the time you travel, this crisis will be over and the service will be running smoothly again. But they've had months to fix things and there is precious little sign of improvement, so if you are thinking of doing this option then you need a keep a watching eye on this.