You have definately done the right thing by joining SUAS.
You will get the best insight into the RAF, from which then you can decide to go forward with an application. Being on the UAS means you will already have some advantage over normal 'off the street' applicants, in terms of information and advice available to make a good shot at OASC.
But remeber your degree takes priority. Some people can get a 1st in Aero Eng and do EVERYTHING on a UAS!