I'm surprised at the 380A quoted by VW. Diesels, having a much higher compression ratio than petrols, need a very hefty starter motor which takes a lot of current (my 2.4l Volvo is about 750 amps); are you sure they quoted you for the diesel engine? One with a low current output probably just won't work.
I suggest you go on a couple of online sites such as Halford's and Euro carparts, look up your vehicle and check the batteries they recommend. You didn't quote the year of your car, so I guessed 2000 just to get the 1.9 diesel engine, and one battery was 800 amps.