Hi Lucie and welcome to planDisney.
It's always a pleasure to be able to help a fellow UK Guest with the planning of a visit to The Most Magical Place on Earth -
Walt Disney World!
Whilst it is indeed possible to purchase Annual Passes from the US version of the Walt Disney World website, sadly, it is not, from the UK version.
You are, however, absolutely able to purchase Annual Passes on your arrival in the US via the US version of the Walt Disney World website or, in person, at a
Guest Relations location at any Theme Park or, the
Disney Ticket Center at Disney Springs.
Although I, myself, have never had an Annual Pass, I understand that Annual Passholders are required to
call the Annual Passholders line in order to add a
Disney Dining Plan to a Resort Hotel reservation and that this must be done in advance, anytime before check-in day.
To give you an idea of price, I would recommend that you check out
this answer provided by my planDisney pal, Ashley F. a few weeks ago. Do however bear in mind that prices are always subject to change.
I hope that this information has answered your question, Lucie. Please feel free to re-visit us, here at planDisney, if we can be of any further help with the planning of an upcoming trip to Walt Disney World.
Wishing you a magical holiday filled with memories which will last a lifetime!
Emma