hi on the way back from holiday yesterday my rs started to hum from the rear .it can only beheard from 35-40 mph upwards. i've noticed the rear brakes are as hot as the front wheels when i took a slow drive down the shops earlyer.could this be wheel bearings as i needed new wheel bearings for the mot in april as they had movement.could the garage just bodged them to pass? as my rs has only done 2500miles since then.or do wheel bearings ware more if the car is lowerd -60mm on 17" wheels

many thanks