they're adjustable. You should check the fronts fairly frequently for oplay and tighten accordingly. i never really bother with the rears which don't give much trouble.
remove youor wheel and the little black knock off centre cap. Under there is a 17mm nut if I recall the size correctly. Rem[ove the split pin and wind thte nut in a little. There are two holes you can put the pin into, select the one that suits the 'tightness' you want in the bearing. After greasing and tightening, run the car for a few miles thene recheck, they've usually got ta little loose, i tend tot do mine on the tight side to avoid the disassembly required due to thie movement of the grease.
i expect you don't need new bearings at all. PS, worth avoiding listening to MOT gargaes where 7's are concerned. If in doubt go to a 7 specialist for verification (or a club meeting)