^^ what Dom said!
I got an initial offer of £550 for my MK2 GTI, and held out for £900 eventually. The truth is that you will never get as much back as you want.
If you want to make the money back without going for compensation then your best bet if you have room is to buy the car back and break it.
Even if you don't claim for injuries, make sure you at least put a claim in for your excess and expenses!
Remember: the car is still yours until you have accepted the offer - make sure they don't take it away without telling you where it is going! Within an hour of phoning the insurers to report my accident, the local breakers came round to pick it up to be 'valued' and 'disposed of in a hassle-free way' so I sent them packing.