Hi
As Martyn has said every case is different and therefore depending on injuries and other issues with the claim some claims do take longer than others.
I would assume if you have had your medical reports, provided they give a good prognosis and it is decisive and not recomending any further medical evidence then your solicitors would want to settle just as much as you do. Don't forget they dont get paid until you do either.
So I would also suggest chasing them up on your claim, if you have approved your medical report ask if they have disclosed it to the defendant. If they have and more than 21 days has passed since then I would assume they would want to issue proceedings also so that they would get more costs for dealing with your claim. It may be a case where your claims have simply slipped their diaries.
Speak to them and ask them for a full update.