Hi AngryDave,
I'm currently preparing for OASC too. There is a back issue of 'Air Forces Monthly' which comes with a free poster listing all the major Sqns of the RAF, UAS, and Glider Schools etc with some snazzy illustrations, and details of EAW's, a few dets and aircraft roles
. Its still fairly accurate, although Jags are no longer at Coltishall. You can order it from the publishers website. Hope that helps.
Sorry, but can't remember which issue it was, but it says on the image of the cover that the wallchart is in there. Jan/Feb at a guess.