When you go to view the car, look at the V5 as it should say it’s a cup on there.
Or make a note of the VIN number and phone Renault as they will be able to confirm.
Also check the paint code is it will either be Mondial Blue or iceberg silver if it’s a 172 cup.
While you can modify a standard 172 to cup spec, most wouldn’t have bothered so if the car has a basic grey cloth interior (rather than the half leather, half suede one), no abs, multi spoke Speedline Turini wheels, halogen headlights rather than xenons etc. it’s probably a cup.
Or post details on here as we’ll probably be able to tell quite quickly