Just a wee update in case anyone else has similar problems with their vectra!  Apparently it has something to do with the fuel line-a return valve that regulates the fuel pressure.  We have tried different valves from breakers but was still doing it so did a little DIY on the fuel line with a clip and it has done the trick for now.  Possibly would be remedied with a new return valve but haven't got round to getting one since problem has been sorted for now!!
                 Carabbie
                
 November 2007