The 18″s that I’ve put on are all 8j ie all tyres are the same size.
Or go smaller – 16 or 17.
Wheels and tyres will be considerably cheaper.
Picked up a set of 16s and got some Bridgestone winters for a little over 300
Do you have the tyre pressure monitors in the valves?
If so they can be expensive on another set of wheels.
If not, happy days – get on ebay and get some second hand alloys – they will be cheaper than new steels if you look hard enough and then get some suitable tyres from an online place. Tyre leader were pretty good for winters last time I looked (it is over 12 months ago though).