You need to check the current legislation, because there was talk of introducing compulsory insurance even for laid up cars as part of the insurance bureau computer database. I'm not sure if it was brought in though. For many years I cashed in the road tax over winter and put the MGB on laid up cover, but in the end I became fed up with the hassle and left it taxed & insured. Mind you, the premium was only £140 at that time.