If you have the grille enclosures then all's well. I take it you don't then you can either: try VAG for the parts - Motolec in Reading advised me they were about ?10 each, try breakers - you'll need a bit of luck to find good ones, or as I did on my Jetta, locate some 4" speakers with square grilles, and carefully remove the door pockets (door card off the car), remove the back of the bin, with a jigsaw carefully cut out the hole, and self-tap the whole assembly back together. To keep the wiring sweet, if you're removing the old 3.5" dash-top speakers, cut off the plug on the speaker, and solder your new run (to the door) to that plug. Therefore if at any stage you find a set of 3.5 replacements (which are out there at around ?40 pair), simple plug-in job. I always try to keep the OE loom intact wherever possible. You can still use the dash-top grilles for tweeter mounting, as has kindly been done on my B/B GTi. Try ebay for speakers as there are some good deals on there.