To be honest mate I've found the traders on ebay just as good as anywhere else. They obviously buy in bulk so there prices are quite low on the replica stuff. Also try flicking through some mags, millions of adverts with pictures!!
Just make sure they are suitable for the bulk of a T4 and you'll be fine!
I can recommend Rochford Tyres near Southend. They are on Ebay, as well as Online, compare the prices as they can vary. Their site has a nifty 'see what yer van looks like ' feature. www.alloywheels.com
I went there to have the wheels put on. Friendly bunch. Would go back again.