It will very much depend on the condition and exact model. The mk3 is the least desirable generally, and overall values are not particularly high. With plenty of decent photos & details of the car's history, I could give you an idea. I wouldn't do a formal valuation without inspecting the car personally.
I don't know where this post has been, but I'm sure it hasn't been in this section for 2 weeks?!
A mk1 is a very different car anyway & is likely to be worth more than the mk3 (depending on model). They top out at about £2000 for a mint one (I'm not talking about insurance value), so £3k is slightly ambitious if you need to sell it.