Don't accept...definitely go down the legal route with professional representation...
Having been involved in a serious motorcycle accident...I also had an offer direct from the guilty parties insurance ...offering to settle the compensation claim with a return cheque.. if I accepted their offer..
I informed my solicitor who advised them, that he would see them in court,,,
The day before the court hearing ... they came back with a second offer...four times that of their first offer..
I accepted.