I added remote central locking to my Fiances Polo – a used remote key was about £15, including a blank blade, cuting was about £20 but it was right on my doorstep, could have got it cheaper if I’d shopped around. A blank transponder chip was about a tenner. Provided you have at least one working key you can program a blank transponder by having the new key in the door while you start the engine with the old one (or something along those lines).
I had to replace the key on a 54 VW T5 a few years back. The only place i could get it was through a main dealer. From memory the physical key was something like £120 and it was £60 to program it in, so £200ish.
I have just been quoted £80 by my friendly independent and £144 by the main dealer for VAG. Unfortunately, the friendly independent is a way away and will need both keys, rendering it somewhat difficult to collect the car in the evening.
I had a mobile locksmith and cut two keys for my 54 plate T5. If you can do without the remote, is you’re capable of putting a key in a lock and turning it, it’s about 60 quid a key. Remote is about a ton.
You should be able to key it for less if hunt around ebay. You need two parts: 1) a key blank – ebay £4. Then get this cut to match existing key. I go to Bury St Edmunds market who charge £5 and do a great job. Then you want the electronics. For this buy a second hand key fob off ebay – about £15-20. You need to reprogramme the key fob to match your cars central locking and immobiliser. The lockng is easy: [video]http://www.youtube.com/watch?v=lb0UdmAVmz4[/video]. This site gives info on the immobiliser.