Reccommend a company who will insure a car using the Chassis number?

This is fairly easy to do if you use a broker. I would recommend you try a broker who is based near an army base. This is because they frequently have UK armed forces returning from Germany and bringing cars they have bought in Germany or which have BFG registered. They need to reregister them with UK number plates so get the initial insurance on the chassis number as you are wanting to do.

Try Forces Financial on 01748 834848 who are based in Catterick, bear in mind they will want you to take out an annual policy and if you cancel it before the renewal there will be a biggish cancellation fee so it will be best to stay with them until renewal.

Not at all, they will have chosen their name as they are near an army base so want too appeal to all of the military there. They will have no problem covering a civilian and will have a customer base that includes the military (At Caterick and all around the world), local civilians and retired military (All around the world).

Give them a call, a broker will not charge you for giving you a quote or some advice, if you decide to take cover up they will be paid a commission by the Insurer (They may have a small admin fee on top of the premium).