go to the breakers in wokingham, near bracknell.. they have a few mk3's.take the parts off that you want and then they will be cheap..as for older cars..the parts are getting more expensive as most people drive new cars...
or just buy a donor car for a few hundred quid and you will have everything you need...
i replaced the auto transimission fluid and filter (£50) exhaust (£50-new) coil pack (£20-new), wiper arm (£10-used),
engine oil and filter (£15) pollen filter (£7ish), used tyres fitted (£40)..
as you can see the car may not cost you much to buy...but will cost you somewhat to keep it running...and this is just a small amount...will have to change dizzy, leads and spark plugs at some time in the future (soon-obviously all will have to be new..)
bulbs every so often (last year £10)..
really if you are worried about the cost of driving this car then you should factor that they are not economical by a longshot...
However on this forum you will be able to get parts cheaper than new and maybe a bit more expensive than at the local scappie...
So you can cut your costs...I could've picked up a used exhaust for my car...but just too far away from me...(200miles) so then a new one is the way to go....
Don't worry so much about the windows....my back ones have not been working for some time...you can get clips cheap from the scrappie if you take apart the door yourself and probably a new clip will cost you a pound tops...or something like that...
So just relax....there are cars in the scrapyard waiting for you...
I've got a B4 passat estate...trying to find parts for that are extremely difficult and golf parts are easier to find..
The scrappie have some good exhausts...stainless steel...etc...just as mine is an automatic it is more difficult to find spares that are particular to that car..but the scrapyards are full of gti's...they outnumber most of the other golfs....
Yeah the prices are high that they are asking for...just go to another yard and you'll be ok...
post in the wanted section and maybe you will find trims and other stuff for an affordable price....if the car cost you £200ish or so then you can spend some money on getting it in the shape that you want...