For track / race only bike insurance you are best off approaching a specialist motorsports insurer as it differs to normal road bike insurance. Bemoto do a good policy which covers Fire, Theft and In Transit cover. They also provide trackday insurance to cover you whilst on track, but it is expensive (when you consider the excess) and normally just covers single events. Moris Insurance also offer similar policies.
With regards to either company you will have to phone them directly to discuss your specific needs and requirements. I've used both companies in the past and they are good to deal with and are very knowledgeable and helpful.