The way the system works now is that your GP will be funded by an NHS Trust. Quite often these trusts operate within county or city boundaries. You will need to see your GP to request a referral to a specialist. The system varies from there on. Some specialists accept direct referrals. The Nottingham clinic referred to appears to do this. Others, such as Charing Cross (now officially known as WLMHT Gender Identity Clinic), do not. They require a referral from a consultant psychiatrist.
Waiting lists are unfotunately several months long.
This is as good a list of gender specialists as you will get.
Your GP may not know to whom to refer you. A typical GP will only see a few transsexuals during his or her career.On my first visit we sat and searched the internet together or ideas. Fortunately he got it right. I was referred to the correct place for my region first time.
Hope that helps.