For the first course or so, staying in Westby Road is really a must. Then you have plenty of opportunities to 'get together for talks and study', or more so socialising down at the Seagull. If you then rent, do it course by course, taking 3 month contracts, there's plenty on offer, even try holiday flats etc.
Some N.I security clearances do take longer than the start date, all that happens is that you don't get a permenant pass until your cleared, its just a pain in the arse every morning getting a temporary one.