Way back when I started most people just started at the top of the list of B&B's and kept phoning each one until one said they had space. For the first course any room will probably do as you'll be seeing lots of the town if normality is followed, so for a change size doesn't matter
Once you have got to know your course mates you can then go and find a place to share for the next course, there is normally a good range especially as for you it'll be the wintertime.
Bournecoast flats in Christchurch I can really recommend, you can get 2 into the flats (or 3 if you manange to get lucky
) and by getting 2 or 3 flats you can have a great laugh. The bills are just for electricity, and didn't come to huge amounts unless you like it tropical!
Well done and most importantly enjoy it.
5mb