These are 205/45/17. I don't know how much the car has been lowered. See other pics taken at the Sywell meeting. 17"x7" have been used by quite a few Amazon owners and seem to work OK. I think 18" might cause rubbing problems as well as poor tyre choice. You would have to go below 45 to keep the diameter down.
https://www.volvoforums.org.uk/showthread.php?t=298650