Thats exactly what we did. Got offered £500 for the MX5 in part ex so rather than miss a minter Zed we decided to SORN the 5 and flog it in the spring.
I'll just get insurance on a month policy in april (gonna cost what.....£40?)......6 months tax and flog it.
Comparible cars (spec, age, milage ETC) we're selling for 3k last spring so I'm buggered if I'm flogging it for next to nothing mid winter.
Basically unless the White Witch's sleigh brakes down and she needs another motor you've got no chance of getting a decent price.