for the future reference of anyone who might be interested, i have found 3 options
http://www.agentfiamma.co.uk/fiamma-vw-t5-bike-rack.html fiamma. the 'budget' option at £281 plus postage
the slicker looking and functioning http://www.roofbox.co.uk/scripts/rbvehsel4_tab.php/car-specific-accessories/atera_linea_bike_carrier_ar4706_package_for_4_bikes/eJgJE%60zLBMrQ%60vx0ICezX5~hSwyjNnjkdjjUDqK,9MMb%60Z5wkW2CTeHRaHSEkFS atera. at close to 400 knicker...
the proper vw one http://www.volkswagen-vans.co.uk/caravelle-range/caravelle/accessories/ at 475 quid.
for the 75 quid difference its probably a safer investment to get the actual vdub one. possibly. although i think the fiamma is closer to my price range.