xl tyre being the same speed rating is the main thing mate. we often up the speed rating on cars at work ie 205/55/16 91h - 205/55/16 91v if there on back order
on a mot im sure they could only give you a advisory if they were mixed
The requirement is on type, size, and structure only
225/45 being the type, 17 being the size, and radial being the structure
Speed and load ratings only apply to MoT tests for Class VII vehicles
i can get you a number for michelin tec when im back in work tomorrow if that helps mate