Hi - an update for anybody who interested.
On the Beverage package page there was an option button to book online which brought up a web-form, and the web-form actually quoted $21.95 for the UDP .... so I rang Azamara.
Upshot was web-form is out of date, price is $23.95, an indeed you cant use OBC to purchase the Ultimate Drinks Package before you board, but I could purchase via credit card over the phone.
As my booking is in sterling then any pre purchases will also be in sterling and I was quoted a sterling price of £181.50 per person for 11 nights or £16.50 per day, a USD conversion rate of circa 1.45 ! Given the dollar has reached parity with the Euro this week I decided to buy now with the option of cancelling later, but at £16.50 a day I'm happy.
Whilst not a FOREX trader I sense the low sterling price is because they are effectively buying sterling to charge the price in my local currency, and right now going from $ to £ is much cheaper for them.
So for anyone who will be charged in sterling now may be a good time to make purchases !
Regards