Hallo - good choice!
Havn't a clue about the accom question - phone Sussex and ask. but don't worry too much about this aspect - there is never a shortage of accom on/off campus and this shouldn't be the only factor in making an Insurance choice.
Yes, Sussex is lovely - small, very friendly and full of 'normal' people if you know what I mean..... no posh 'okay-yahs'.