I can get these set in mint condition locally for less than $150.00.

They are 15x8 ,5x108, 42mm offset.

I currently have the standard 17" OEM wheels.
I do not know how to photoshop and superimpose the wheels onto the XJ8 to see how it look.

 

Even if the bolt pattern is different, which I doubt seriously is a problem at $150. for all 4 they're a steal and I'd double your cost AND pay the shipping if you're in the U.S.

They are 18" correct as your title says one thing but your message says 15" X 8"