Funny, I've only ever had trouble with two sets of taps that I've fitted and both were B&Q.
As for power tools I've completely the opposite opinion as you do - I find their Performance and Pro power tool ranges to be truly excellent quality (particularly the Pro) and well priced. Have you actually used any of their stuff?
Their SDS drill I got for €75 pounds through concrete in the exact same way as the Hitachi we used on sites. A skill saw with laser guide and blade for €36? Its not makita but its a steal at that price and has glided through the hundreds of feet of 3/4 inch ply I've been using it on. Their Pro chopsaw (admittedly only bevels for mitres on one side but I've gotten used to it) comes with laser guide and 3 year warranty and all for €193. Again, its not up to the standards of the DeWalt we used on site but since I've left that game and the tools are all for use on the renovations and extension I'm doing on my own house its a great deal. I'm 100% convinced that their Pro range, or at least some of it, are re-badged Ryobis, which anyone in the know will tell you are a rising force as their quality is a lot closer to the DeWalts and Makitas etc than their price would suggest (and the 2yr warranty is great).
I could go on, but the bottom line is the B&Q Performance and particularly Pro range are far, far superior tools to anything I would class as fit only for the DIY range e.g. ROK, Black&Decker, most Bosch stuff.
Anyone buying a DeWalt chopsaw is probably still in the trade, in which case they'd know they'd be mad buying top end gear like that in B&Q cos they could get a better price through the building suppliers where they have their account. A particularly savvy tradesman would buy online, where he could get the DW 708 for the great price of €804 from
http://www.tooled-up.com/ManProduct.asp?PID=1614&MAN=Dewalt-Dw708-240v-Double-Bevel-Mitre-Saw
I've no affiliation to B&Q and think their kitchens, sanitaryware inlcudng taps, are muck.