Yes use wise all the time and never had a problem. Also check out the Wise Thailand FB group and you’ll learn how to transfer funds from Thailand bank account back to home bank 😉
I expect that the airline will stonewall you hoping that you will disappear over time. Now is the time for UK261. Once you have submitted the UK261 let the airline know as that may get them to revise their position. Another cheeky option is to go straight to the inbox of the CEO. There is a prominent site for many CEO email addresses (won’t post the link here) it will be intercepted by one of their execs who will give it the due attention. Good luck.
I assume Belfast was the originating point? If so you are protected within the UK regulations for compensation under UK261. Raise a claim via that route, if the airline still refuse, lodge a MCOL. It will be a hassle but you should be awarded full refund and costs.