They're one of the most reputable wheel sellers going in the BMW world, so no worries there, for me the price is a little high. You could have a superb refurb of your own done for £500.
I have a set of 108's off of the car at the moment, already split down, I'm about to get those all sorted and refurbed in the same manner, I'd probably have them sold on for £500 to give you a guide price.