spacers will work but you will need around 10mm ones, and ideally you would need new longer studs too. or alternatively get the wheels centre bore machined out, but you will need an engineering shop for this and i would imagine they would want the tyres taking off before they do them.
both ways cost a bit, spacers about £20-25, longer studs £about same, so around £50,
machining £10 per wheel ish id say.
is it really worth it for a set of astra wheels?