Try to start giving them clues. For instance, I started voicing my opinion on certain social issues. I didn't ask for their opinion, I stated mine so they knew where I stood. I'm not up on UK issues, but I thought maybe something you could mention would be that kiss-in at that London pub? It was a while ago, but that would be an example of something you could bring up in conversation.
The other thing is maybe when you are leaving to go on a date, mention your bf's name as who you are hanging out with.
You'll kind of know when you're ready to have a conversation. There are a lot of threads here, this one in particular was really helpful or at least spoke to me:
Coming out some more.
I found reading a lot just mentally prepares me. You can then even write out what you want to say. Try to anticipate questions and work up your responses. I know some people prefer letters, it's all about what you feel most comfortable with.
Remember to be careful with your emotions, because you'll want to set the tone and keep it respectful to you and them. Also, they might need time to think about things and come to an understanding/acceptance.
And remember, it goes down like nothing you planned. :tongue:
Best wishes!