When i had my ST170 the standard ford brakes warped all the time but that was due to driving it like a hooligan lol and getting them glowing like this:-



Also the mondeo i have with similair size 300mm discs, i replaced with genuine ford ones and these are also slightly warped also.

When i had the ST i put tarox discs on and it was fine for 30k with hard braking.

Id def say the cheaper discs wont last long at all.