But lots of gyms (often those attached to pools) do have changing villages with individual cubicles. There are 8 gyms run by my council, 5 of them (the new and refurbished ones) have changing villages with individual cubicles, 1 has both that and separate male/female, only 2 have just male/female. I know people dislike them but they're becoming more and more common and tbh there are advantages for other groups as well -parents taking opposite sex children, etc.
All also have disabled facilities although I don't think that should automatically be the first alternative and sometimes the disabled changing room is inside the male/female.
Only specifying to clarify that even if every single gym follows what it seems the new echr guidance it's not as though that means that every trans person in the UK won't be able to visit a gym ever again, as OJ is catastrophising.
They can join a gym that has alternative/unisex facilities
They can campaign for all new gyms built to have unisex facilities (like women had to when there weren't any loos for them, like disabled people had to, etc.)
They can just change before going to the gym -I literally never see anyone use the showers etc in my gym (pure gym) anyway.