Hello Katie,
How exciting to have a whole 21 night holiday at Walt Disney World Resort to look forward to this coming September and on top of that...the possibility of an April 2015 trip as well, lucky you!!
UK Guests wishing to enquire about upgrading their
Ultimate Tickets to the
Walt Disney World Passholder Program should speak with a Cast Member at any
Disney Theme Park Guest Services.
The Cast Member assisting you can then calculate the upgrade costs pro-rata by seeing how many days are left on your 21 day
Ultimate Ticket against the price of the Annual Pass you wish to purchase.
With this in mind, I suggest seeking the advice of Guest Services at the very beginning of your holiday rather than at the end when you will have used up the value of your 21 day
Ultimate Ticket. If I can help you further plan either of your Walt Disney World Resort holidays please pop back to ask me another question.
Have a great Disney day.
- Jane