There are plenty of Insurers who will offer cover although most of the direct companies won't be interested as they like standard business that can be transacted with minimum of fuss.

One of the main issues for Insurers is whether all of the work has been carried out and that it is to a good standard. It may well be worth getting an independent engineers report to this effect which will normally satisfy the Insurers that will accept a Cat B car and future purchasers. (This is not the type of report that RAC etc do for the purpose of buying a car).

Your first port of call should be local brokers and specialists such as Flux, they may well not need the engineers report so hold off on a report until you know whether it's needed or not and what specific information they may need the report to state

I thought that a Category B could be used for spares but the bodyshell should be crushed.

Has this car had a new shell, using parts from the write-off? Or is the usual guidance that Cat B's may not be sold for use on the road incorrect?