Thanks jim anyone have any idea what offset ect I'd need to run 15x8s on the rear and 15x7s on the front I have no Idea when it comes to this stuff unfortunately
If unarched, I'd go +12 on the front (although you can squeeze +6 if you roll your arches and your tyres aren't too wide). On the rear you'd need to push the extra width inboard, meaning something like +24p. Personally I don't see the point of that, so I'm sticking with 7" ET12 all round.
Wheels are expensive, so check that these figures work for you before you buy. Measure, then remeasure etc.