i had this problem when i bought my mk4 gti, i was told that most mk4 gti`s were pre wired to take a cd changer, but when i looked i couldn`t find the wires to plug into. luckily one of my mates worked for the local vw stealership and he came round to have a look and told me it wasn`t pre-wired but he had a wiring loom so i could connect a cd changer asked him how much a cd changer from vw was and he told me around ?400 for a vw one, so i bought one off of ebay for ?125, phoned him up he came round and fitted it all for ?40, i think the wiring for a cd changer is about ?50 from vw. the other way you could go is go down halfords or any good stereo shops and they could sell you a cd changer, wiring, and conversion box(so it works with your vw stereo) i dont know how much these are but just ask at halfords etc and they`ll tell you a price for buying and fitting, hope this helps
