well it didnt turn out to be the rear right wheel sensor.after chatting to a few people i know in vauxhall i decided not to change the hub, but change the ecu as they said it was very unlikely to be the hub.
the trick now tho was doing it with out removing the entire abs unit, and what a sod it turned out to be.
as you will see from the below pic it sits in a bracket, this bracket has a locating lug underneath it which fits into the bottom of the abs unit so you have to un do all the bolts (5 in all) that hold the bracket and abs unit in place, carefully lift up the abs unit as high as you can so it comes away from the locating lug, then giggle to bracket around untill it comes out at an angle from the back.
then you simply undo the 6 small bolts that attach it to the abs unit and change the parts over.
it was prob one of the more difficult jobs ive done, if only because it wasnt realy designed to come out without the abs unit first being removed.
any way the fault has now cleared so it was the ecu and not the rear wheel sensor!
jobs a goodan! :thumbup: