Maybe a bit late but if it wasn't his fault he should claim straight from the 3rd party, not involving his own at all, other than to inform them of this.

If its written off his current policy would have been uninterrupted and just needed the car change over.

If he has claimed under his own poicy it could be negotiated with them but very doubtfull they will continue but could be claimed back as a consequential loss through no fault of his own.
valuing the NCB value wont be easy but a value over the next 5 years (as thats how long it will affect him) should help pay for the next policy i'd imagine. FFRR MY06 facelift With TDV8 Alloys Zeros/ATR's
Mantec Sump Guard, Rigid Load liner, MY10 BT upgrade.