I don't think that the fact you are serving makes any difference - I'm assuming it is not information you require in the course of your emplyment?
That said, if it's something uncontentious/historical an informal approach to the FOI folk may grease the skids. This is based on my submitting a 'pre-agreed' FOI request when I was working as a CS in MOD.
You write a letter and hand it to whomever seems pertinent. Technically it doesn't even need to say FoI in it, but it helps. Any employee is bound by the requirements and must either fulfill it or pass it on. Their policy should be fairly well documented, ours is.
Just remember, that if it involves personal data, that's a different matter.