I can remember 20 years ago feeling I had to buy the Tranny guide to identify shops in London that would allow me to try stuff on. Now I go to places like the supposedly traditional York and the N of Scotland and seldom encounter anyone who is not completely accepting and helpful. It is VERY rare to be refused to try things on when dressed as a man and no problems of any kind dressed as a woman. I remember asking Long Tall Sally in Aberdeen (now sadly closed) if they get many men buying for themselves and they said it happened so often they regarded it as normal. OK, I still don't fell I can go to work in a skirt or dress - not because it would not be allowed - it certainly would - but because of possible impact on my professional credibility. I might be inventing this last bit and failing to give those I work with insufficient credit but I would rather not take the chance.
So not mainstream, but very accepted.