Cadoc is before the gic right? Mine went like this....
'No I don't really need to ask you any questions to refer you for gender care, if you tell me you have gender issues, you have gender issues. This step is pointless, I wish they would stop referring to local psych, they don't need to.'
I doubt it will be very involved. They will see you once and sign you off with high probability. This step has been removed from recommended practice for a reason; it's pointless.
Do yourself a favour and ask for Northampton or Nottingham instead of charring cross as the wait times are lower. A lot lower. Northampton is the lowest in the country I think.
Grab a copy of the interim guidance on gender care and familiarise yourself with it.
For the first gic visit, how it will be and what they will expect you to prove is dependent on the person you see and the general approach of the gic.
I don't wouldn't expect them to be interested in getting to know you. They will be interested in ticking boxes. You will probably only see them for a total of 3 hours or less over a year, so they wouldn't have time to get to know you.
They will want to see, if you have it, name change proof, change of document proof, pay slips with name change proof, yes, they will judge you on your presentation but that doesnt mean andro ppl won't be treated (though they often report having a slower process with more visits).
They will ask you to talk through your history, ask you about general physical and mental health. They will ask you what you want from them in terms of surgery and hormones. They will be looking for consistency with that over the coming visits and in how you felt previously.