On my course (started in March 98) probably half had not arranged accommodation prior to meeting on the team building week, and grouped together, rang around and organised things then.
I didn't advise against renting, many have and do, but be aware that you might not want to commit to a definite six-month lease. Perhaps you can rent somewhere for a shorter term, or perhaps a more flexible lease?
I stayed in a B&B the whole time.
About the PPL, I don't know. Most haven't flown before and the 15 hours are spent going solo and general handling, SSAT. I had done a bit of flying previously, so after I went solo I did a lot of dual cross countries and ILS /SRA approaches, VOR holds etc., stuff that we decided would be of more use from an ATC point of view. I know one guy from my course already had a PPL, and used his hours to get an IMC. I guess it depends on where you get sent for the flying, and how willing they are to adapt the programme around you. I went to East Mids (Sorry, Nottingham East Midlands Robin Hood Regional Doncaster Tees Durham or whatever it's called this week). and they were fab. The six of us had sole use of the flying school for ten days.