Yes, it's an interesting one. UK anti-spam laws really only cover contacting consumers (ie: Joe Public). As far as I am aware, there is much more flexibility when it comes to contacting businesses, so long as you give them the opportunity to refuse further mailings from you.
http://news.bbc.co.uk/1/hi/technology/3120628.stm
It's easy to spot the difference between someone who has spammed you from a mailing list, and someone who has researched your business and has chosen to email you about a product/service that they genuinely believe could be of interest to you.
I suppose it's a thin line between unsolicited mail and business generation. Lets try this as a hypothetical example ...
Someone on this forum runs a website selling iPods. Someone, somewhere has a great deal to offer on wholesale iPods. They've researched things, know you specialise in that type of thing, think it's very likely that you'll be interested. They send you a mail explaining what's on offer. Is that spam, or not? I reckon it's just a business proposition.
Of course, all of this relies on people being sensible and putting in the hard work to find potential customers.
Ali.