Sorry, forgot about the master key..
You should very rarely need this.. I had the car battery disconnected for more than three months and the engine out for tuning and I never required the key for anything. By looking at other people's misfortune though it looks like it's more down to luck than anything! My advice is be afraid.. you won't know when the CODE will strike and when it does you'll be buggered for good measure! You'll need a brand you set of locks (£56+VAT) on top of a new ECU (£400+VAT - correct me if I'm wrong). Don't forget the labour either since fitting the new locks is a nightmare. Only very few people outside of dealerships have got the experience to do this kind of job.