Wheels

 by the way they are 5 stud

Not sure what size you have at the moment, but bear in mind, any increase in rim diameter, will require a reduction in the tyre profile.

The lower the profile, the harsher the ride (generally)

 

This site has a pretty good tyre equivilent calculator, which also shows % difference.

https://www.oponeo.co.uk/advice-and-tips/tyre-size-calculator

wheel info

I have a set of 18" for sale that will fit. They were fitted to the Mazdaspeed kit cars and were an option on all NC1 from new. They are Option 40