The Bilsteins are great and I would say that the anti-roll bars make a subtle, yet noticeable (and worthwhile) difference. It's nice to be able to corner a bit more like a car. Admittedly it's a bit more like an astra, rather than a ferrari, but at the end of the day it is a heavy van and it's reassuring for it to feel like it's not going to topple over.
The H&R antiroll bars do need the rear auto-levelling light sensor bracket adapting, but any decent garage or mechanic will be able to work it out.
In terms of wheels!!!!!!! I agree, it is a total NIGHTMARE getting good looking wheels with the correct load rating for a T32 (860Kg rear axle).