Thanks for the heads-up about the buses out of season, etc. We are travelling in December 2023 so might be the same issue, although the train I speak of is supposedly dedicated to Costa customers only.
That said, I was only considering the excursion because of the predictability/reliability of public transport. However, if the trains are reasonably reliable and we can plan our trip into the city and back with some degree of predictability, we will probably sack the excursion and head straight to the station ourselves.
Thanks again