No problem with them fitting physically, but not legal.
A 15" tyre does not have the load rating to suit a GU.
(Off the top of my head) A GU need a 112 rating the most you get out of a 15" is 108.
Just letting you know.
A lot of people run 15's as purely offroad tyres as they are cheaper and have more tyre wall height.
Pep