You'll learn to shop around depending on price and quality you want to use, certain suppliers have better parts than others depending on the part, i've used custom and commercial for window seals, vw heritage for general bits and bobs and cool air is my preffered supplier, when i first got my van i used jk.....
Yeah tbh most of the main guys are ok, admitedly all of them may have parts at some stage u may not be happy with, but both jk and vw heritage as well as cool air have been cool when theres been an issue
I've used most of the usual suppliers, not had a problem with any of them I always call Autocraft for panels, cos there stuff is top notch but their parts list for the bay isn't the largest at the moment
I've tended to shop with most of the VW parts suppliers at some point. I've used: Just Kampers Cool Air VW Heritage Custom and Commercial Status VW Machine 7 Kingfisher Kustoms T2 Customs Not had to buy panels (yet!) so haven't had cause to use Schofields or Autocraft.
Coolair offer the guys on here a 10% discount whilst VWH do a 5% discount, Bigrich at Coolair is one top fella & will sort you most parts if you call him!
Schofields are good for making you bits that nobody sells as standard, but they are CRAP and packing large panels. Nice peeps though. Otherwise I ring around at random until I find someone who has all the parts I want in stock. They really do all sell mostly the same parts.
if you get a good one you shouldnt need any ;D but all the above are good if you get what your after n it fixes it.