Not sure if its true but i was told not to accept any cheque from insurance company (well under the value of ur motor) as its classed as part payment allowing them to drag there heals in a battle of wits from then on.
Anyways got offered 7k for a 10k car i wrote off after 6 weeks. Tore the 7k cheque up and sent it back with 'print screens' of all matching cars on autotrader valued at 10 -11k. Next cheque they sent was for 10k.