rumbling sound on my rear!!!

the title sounds naughty but its not (makes a change comming from me.) ok going to pick your brains. got this constent rumble i think from my rear off side wheel but not 100% i could be wrong. its not really loud noise but once you pick it up with your ears you know its there so to speak. when i bought the car it had just passed its mot with two new tyres fitted on the rear cheap nasty things. anyway i got it to a garage the other day up in the air on the ramps the macanic gave it a really good check over, looking for eggs on tyres, noise from the bearings when spinning the wheels ect.... but said he could not hear or see anything. but said the new tyres could be the cause with road noise. ok so i put the new set to the front and put the front to rear. still fooking rumbling. any ideas guys before i take a lump hammer to it

ok i know its a volvo, but a wheel noise is a wheel noise no matter what car it is