I did the same as Dan Turner ~ phoned PMC, asked them what they use and bought the 6mm clear-jacketed van Damme stuff. The PMC website also mentions van Damme as their cable of choice, with the sensible corollary that you can spend tons more if you wish, but doing so is unlikely to achieve better performance ~ different, maybe, but better probably not. If anyone knows what they're doing when it comes to choosing speaker cable, it should be these guys after all.
Over the years, like many audiophiles, I've tried all manner of fancy cables, none of which really justified their fancy price tags. For quite a few years I was pretty settled with 13 amp twin & earth mains cable (I recommend it as a reference relative to anything else you may try). But then I acquired a pair of PMC IB2's and figured I may as well get the proper cables to go with them. That was the only reason I changed, really.
Anyway, these van Damme cables are down to earth, quality, no-nonsense cables at a very modest price and do everything a good speaker cable should, not least when you're emptying down them most of what a pair of Bryston 7B-SST's can dish out.
I never held Julian Vereker in particularly high regard (given that Naim was a leading light in the 80's hi-fi mafia), but I did agree with his opinion that if you want to spend extra money on your system, then it's better to allocate it to higher quality electronics (and not just yet another Naim power supply) than to high priced lengths of wire. Naim's own multistranded copper speaker cable at just £5/m was/is pretty good and I lived happily with that for a few years. Now I use biwired van Damme speaker cable. It's at least as good as anything I've ever tried previously and cheaper (not merely less expensive) than virtually any other cable. Pay more if you like, but IMHO there's really no need.