B&W are not stocked at variable prices. The price advertised by one retailer is exactly the same everywhere. Some places may offer you extra's into the bargain like speaker cable, or if you are spending a lot of money you may even get the shop to give you a small discount.
A £60 sub cable thrown in for nothing is not a bad deal. Consumers these days are far too picky for their own good. Considering the time, advice and aftersales service given by most reputable high street dealers that most customers dismiss without even a hint of gratitude its a surprise that Sevenoaks and other stores even bother carrying on.
I got my asw675 from my hifi shop with 10% knocked of the price(£580). Most dealers will if they know you are serious about buying come to some arrangement.The hifi shop i go to is only small but always seems to help out with discounts on all the stuff ive had off them.Only thing is no mail order everything has to be collected from the shop.