EU261 Spain - how to claim from the UK
 

I booked a flight from Spain to Ukraine on a Ukrainian airline. Flight went ahead, but because of likely overbooking the airline told me 24 hours before departure that the flight was "cancelled". I've got the FR24 logs, and various other pieces of data to prove the cancellation is b*llsh*t. Given this, I don't expect the airline to cough up the EU261 money without a fight.
However, I live in the UK, and don't really want to spend the time to go through a full court case to claim EU261 in Spain. The Ukraine has a similiar scheme to EU261, with identical compensation levels
As the UK has left the EU, I can't raise a claim through the EU courts from my home any more. Please don't go on about the B word - I have to live in the real world, not a theoretical world. Bott&Co only deal with flights that touch the UK

Is there any way to get the money enforced, without paying 90% of the compensation value to a lawyer or waiting 3 years ? I had a look at the Spanish AESA website, and it seems like they only want to say what should happen but don't want to get involved in actually forcing airlines to follow the rules. I certainly don't expect any regulatory body in Ukraine to bother to do anything on this. I'm beginning to wonder if EU261 is perhaps a nice idea in theory, but can't really be actioned to actually get the money

Have you had a look over on Flyer Talk Forums? Might get more help over there?