The main thing here, is that you got out OK... i assume? I suspect you would have had heavy bruising at the least!
The car is a GTI and not a lesser model I take it, If so, then push the point that Mk2 GTI are very much sought after, and command a higher asking price, than any lesser model. Do some homework, and get yourself some prices together of similar cars, and have in your own mind, what you think would be a fair price to replace the damaged car with something similar... I wouldn't say anything till they make you an offer! and under no circumstances release the car to the Insurance, without sorting a price!
Thom