Just to follow up for anyone who is interested.
I had a reply from
www.synthesizerservice.de who confirmed that the potentiometers are the same for all virus models, except the rack mounted ones which has encoders.
They can provide these for euro 6,20 each + 8 euros shipping + 19% VAT... which is quite pricey and I'd be keen to hear if anybody has found a suitable alternative from e.g. Mouser?
There is also this guy on ebay who is selling them slightly cheaper:
http://www.ebay.co.uk/itm/Access-Vir...EAAOSwBLlVZ51n
Cheers