Please don't take this guide on this link as gospel 🙁
IE;
Model Year PCD Offset
Vectra 5 Stud 92 to 02 5x110 35 to 45
A 38 offset on a standard Vectra is ok.
A 38 offset on a SRi or GSi is ok if your suspension is in top notch order and don't carry rear seat passengers or load the boot too much,
but forget anything under 38mm if you have a lowered SRi/GSi and you haven't fettled your arches 🙁