I think this is meant to be mate. When Ford set up the FRS suspension they did it with negative camber to aid in better cornering and better handling.

My FRS tyres wear more on the inside aswell, only thing I can suggest is to change them over with the fronts about half wear.

Go back to the Ford sales pamphlet or early write ups on the car and read up about the negative camber suspension set up.

Hope this helps you