GaiPilot,
you received a lot of useful answers and hints here. And I would like to add one more.
I am civil pilot and worked together with quite a lot of homosexual pilots. You would be surprised how many there are. And they are all doing fine, without any exception.
But ALL of them have/had one thing in common: None made a big deal about it - at least not in the beginning. Of course later everyone knew about it and people sometimes ask "well, how is your partner doing" or something like this.
Well, you will agree - somehow you realize if your workmate is homosexual or not, most of the time. You can say by the way he talks, he behaves and so on, at least most of the time. You might not have to tell them. Just act professionally and stick to your job. For confirmation: I am absolutely liberal and openminded.
In your place I would be careful in the beginning. Don't push it. Just do one step after the other and finish your training first. You will then see how people are dealing with certain topics, how things are going there. And later on people surely will get used to a male-mate who is just showing up with a "husband" instead of a wife. As long as you are gentle with it and not provocative. Maybe the commander's wife as well as your future mates will find it rather interesting once they have the chance to make a self-chosen approach to you.
And sure soon you will know who you can trust and when you better have to keep your mouth shut. You will have mates with whom you can talk in an open way.
But for the moment: make sure for yourself if you are mentally fit for a surrounding like this. The RAF surely is not only a bunch of well-trained tough men in uniforms - you will need a certain spirit to cope with them and their assignment. Last but not least when RAF members here in this thread talk about some "banter" you surely will have to bear. Well, have fun...
Then, if you can surely say "yes", just concentrate on your training in the beginning. Later things will solve on their own, I am sure.
And I am sorry for my rather bad English, it is not my mother tongue.