There is the option of laid up cover, but as mentioned above that sometimes premiums for these cars are so low it's worth keeping them insured on the road all year (you just reflect the actual usage in your mileage) - it does give you that freedom of jumping in without having to up your insurance back to road use if the sun makes a wintery appearance!
Either or, we can take a look for you if you'd like and RhoCar are still a recognised club of ours for club member benefits