Spacers will only push the wheels ouot further causing more problems. If the wheels are within the correct offset range with the correct size tyres, the best option would be to have the arches rolled. Failing that change the wheels and tyres for a better fit.
Ill fitting wheels and tyres are so dangerous and upset the cars handling very badly.
Remember this,
The smaller the offset the further the wheels will stick out from the arches.
The larger the offset the further in the wheels will sit from the arches.
The Vauxhall offset range from ET39 to ET49 IIRC.