Try to use it as much as you can in November and December. Unless you've opted for a six-months of road tax, the main reason to lay up a car up over winter is to avoid the salt on the road - and as we don't normally see the gritters out until January and February, you've still got some crisp days to enjoy the car on. Keeping it moving will prevent flat spots forming in the rubber. If you're dead set on storage - make sure all your fluid levels are topped up. We'd also recommend investing in a trickle charger to keep your battery in good health. And yes, we'd suggest using an additive in the fuel tank. Millers make a range of suitable additives and we've used them before.