When I was looking around, the whole price scale tended to be about £3400-£5000 for different levels of cars.
There are some real mint ones, stock spec, but up for too much money, good luck if they can sell them, but generally, i'd say for stock spec, if its an absolute minter, 4k, modified (within reason), anything up to £4300-4400.
I sold my old MK3 black Cupra '51' plate, with 60k for £4200 in 2007, these cars don't get any newer as they stopped in 2002, so I used to base my pricing around that.
But, as always, even if it looks in top condition, these cars will always need something doing to them, no matter how much you spend on one.