I am not from the UK but I just went to my GP today. I really thought I was going to let my nerves get the best of me and chicken out. Anyway, after going through the physical and everything I said "there is something else I need to discuss....." My last chance to chicken out. She says "Ok, what is it?" After 5-6 seconds of silence, I tell her that I have GD and I want to start HRT. Had a good conversation after that and am glad that I did.
Good Luck and I hope your conversation turns out as positive as mine did!