That is very unfortunate set of circumstances, there is nothing can be done about for your planned trip next year with the 241, the expiry cannot be extended.
In the circumstances you can either: try for MFU with the miles already in the account when the seats are released and earn some more miles from the WTP tickets and from the Amex for making the purchase; or start spending to trigger another 241 quickly.
Another option is to get the Premium Plus card where the 241's have a two year life, you also earn 1.5miles/£, but have to pay the annual fee.
I missed out being able to use my first Amex 241 voucher many years ago before I fully understood the system, but have never allowed it to happen again. In fact our two 241's/ year generally get used as soon as they are triggered.