"kerb weight" is no longer a "recognised" phrase ... the vehicle now has maximum permitted weights as laid down on the VIN plate ... can't find an on-line vauxhall piccy .. but this ford one whould do :

4 maximum allowable weights ...
top one : maximum permitted mass - max weight of vehicle (in this case 2235 kgs)
second one : maximum permitted train weight - max of vehicle + trailer (in this case 4235 kgs ... note if you subtract 1 from 2 ... 4325-2235=2090 .. this gives you the maximum permitted trailer weight useful for caravanners to know)
third one : maximum permitted front axle weight (in this case 1050 kgs)
fourth one : maximum permitted rerar axle weight (in this case 1230 kgs)
This link does give some specifications including a "kerb weight" of 1733 / 1713 depending on auto/manual
http://www.carenthusiast.com/ncar0409/omega_s6.htm"kerb weight" used to include driver and 3/4 tank fuel if memory serves me ...
hope this helps
Entwood