cd player

Hi guys, after some help so thought id sign up!!
i've recently bought an P reg Audi A3 1.8 sport, however its got the standard radio cassette player in there and i want to replace that with a cd player but the gap where it goes looks too wide for a standard one to fit. is there a particular type i should look for?
your thoughts would be gratefully recieved.

There are dash adapter kits available that trim out the aftermarket radios so they fit perfectly in the factory spot. You should be able to order one from any local car stereo store. You can also get the wire harness adapter so you don't have to cut any factory wires. The dash kits usually run about $30-$50 and the wiring harnesses are about the same. Hope this helps.