Interesting to see this turn up again!
I've been back to the GUM since for my Hep-B injections and regular testing, and have seen a number of different members of the staff their now, and they've each been friendly and completely non-judgemental - I've always been completely honest with them, and really can't fault them at all. I've booked appointments every time since the first, and have only once seen anyone else there at all.
They did give me a bit of a panic after one lot of tests, when I received the dreaded text asking me to get in touch to discuss my results (so I changed my plans for a punt that day, as a precaution), but when I phoned them they said everything was fine, it's just that I'm one of those (lucky?) individuals for whom the Hep-B doesn't work so well, so I needed extra doses to get my immunity up to what they wanted.
Have to say I did not give this a thought, and I've felt no reaction or side effect from the vaccine myself. To me it seemed a no brainer to have it.
After each of mine I felt a bit light-headed, but after discussing it with them that seemed to be unusual. I just made sure that I stayed in the waiting room for extra time after the additional shots, rather than heading straight out for a bus, and that seemed to help.