205/55/18 and 225/55/18 tyres on same alloy wheels?

I have a small 4x4 (Honda HVR). It came with a set of 205/55/18 tyres. The only winter tyres I could get are 225/55/18. They fit and I drove two winters on them, but I have been advised that it's dangerous. Now I need a new set of summer tyres and want them slightly wider, at least 225/55/18, as my winter tyres, but not sure if I should get new alloys slightly wider for both winter and summer tyres. Is it really dangerous or not? Do they really make different sizes of wheels for every size of tyres?