CTC have laywers who are experts in this kind of thing.
http://www.ctc.org.uk/
They won't necessarily do an awful lot to help non-members though.
Leave it with the police for a bit, in the meantime keep a record of what injuries/treatment you have and any receipts for bike repairs. Then go through the drivers insurance company – if things get complicated (and you consider it worth it) you probably won't have much choice but to get the no-win no-fee vultures involved.
Cycling Weekly has a good list of cycling specific solicitors in the back of the magazine, new issue (Sat 14th) is out in the shops today.
Then consider joining CTC or British Cycling for the insurance cover, it's well worth it!