Hi Robin - I've been wondering the same thing myself. I've tackled a lot of jobs on my car but I think a wheel bearing change is beyond my skillset. I've read the reports of people using 4 metre scaffold tubes as breaker bars! So I had a chat with Tanc at Tanc Barratt a couple of weeks ago. He reckoned around £110 labour per corner, so that's £440 for the complete car, plus materials of course. He cautioned, not surprisingly, that costs could be higher if problems are encountered, for example if damage has been caused during prior repairs.
Cheers, Norm