I contacted CTC regarding applying while still at university.
I got a phone call from a lady (can't remember her name now) but she said you could to the first phase (application) and then if you are lucky enough to get through to the 2nd phase you can then put a freeze on the process and then inform CTC when you are then ready to be invited to phase 2.
I'm just going into my final year at uni but am going to first of all work at the airport (hopefully as ramp operative) and then go and do all my sorta student travelling seeing thw world business then am going to apply for either CTC or OAT.
Best of luck