1. Get 5 litres of petrol, one milk bottle, old rag.
2. Wind down car windows.
3. Douse car with most of the petrol.
4. Put a little in the milk bottle with a rag.
5. Light rag and throw into car.
6. Claim insurance.
7. Buy car that isn't a total heap of shit.
To answer your question, as long as the light is working, and doesn't half enough water floating around in it to support life, then you should be fine. You could always seal it with some PVC Weld glue (you'll get that in B&Q)
2007 Metro Blue 5 door Mk5 Elite 1.7CDTI
6th Vauxhall (4th Astra) in 10 years...plus a couple of other sheds...
I'd only get £200 if I would claim on the insurance lol. TPFT :S