Hey Rach,
The wheels in your picture are Porsche Design 90 wheels, which are 16", which I think is a touch too big for your car.
Although, a quick look through the photo gallery brings up an example with the wheels:
13" and 14" are good sizes for the Mk3, and you can get 15" wheels on there too. In most cases you would need new tyres, as you're buying larger/wider wheels than your stock steelies.
When you're buying wheels, you need to set yourself a budget. Really it depends on how much you want to spend.
Here's some websites:
http://www.dubmeister.co.uk
http://www.swtyres.com
eBay is a good source for used and second-hand wheels. Also, a lot of VW alloy wheels end up on there, such as the BBS RA's as seen on the Mk3 G40.
My Dad tells me that he has a set of brand new Borbet CF's in stock in 13" which will fit your car. They look like this:
He says he can do them for £150.
Hope this helps
