[shiner]

The risk is that should something expensive go wrong prior to you building up enough of a "repair kitty" then you will have to fund that repair.
Also consider, there are many issues that can go wrong that could potentially wipe out three year's worth (or more) of your kitty. A gear box issue for example could cost £5k to fix.

The £1300 you quote. Yes it is a lot. But consider it this way.... Say you bought a newer 535 model for more initial money to get into 535 land. That newer plate car costs a lot more than you paid for yours. And that extra cash you forked out would start to deprecate immediately. If you have the BMW warranty on your older car, albeit at that £1300 cost, you are pretty much covered against anything. The depreciation of an initially more expensive car would be many times more than £1300 per year. BMW know this of course....