Based on your username, I'm assumine you're 22/3 and as such, worst case scenario you could resit your GCSE maths at a local college. Your best bet would be to go in to your local ACIO who will give you the contact details for your local ACA1, whose assistant will validate your qualifications.
Thank you for the comment Yorkshire Lad. I'm more concerned with hearing any comments regarding my question for future readers. (without sounding like an complete arse; I've already made plans to resit the course for Septmeber 12)
Even though the army need to maintain educational standards in officer recruiting; I'm unsure if what difference 1 GCSE will make in my position. (I also know that the minimum standard is exactly that, a minimum standard... The army have the privilege to selected the qualified)
Thanks a lot for the link, this has confirmed my query on the adult numeracy test (I'm assuming that the RAF and Army have very similar educational requirements) and it won't be recconised unless it is a level 3.