What is WebFinder?
As BakedJake points out, it's a PPC engine that is based in the UK. It's owned by Thomson Directories that are one of just 2 Yellow Pages providers in the UK (although they can't brand their directories as YP as there is a monopoly on YP rights in the UK).
Their main print directories are 'Thomson Local' and indeed they do serve a smaller area than the equivalent Yellow Pages directory. They aren't as successful as Yellow Pages but they seem to do O.K.
As for their online properties, they also seem to be behind Yell.com, however they seem to be looking at how they can improve and I'm discussing something big with them in regards to local search. Their PPC engine is gaining a little momentum but they do have a long way to go before they have a good coving of advertisers for most categories.
Local Search is a big buzz word for both www.yell.com and www.thomsonlocal.com as they BOTH use 'The UK's Local Search engine' as their strapline!
Now I just need to convince them to put their trust in my company, this may be trickier that it seems. In the UK there is a completely different attitude to database licensing, Yell and Thomson seem to think that they should keep their duopoly and make it expensive for others to gain access to any type of good quality YP/business database (especially when you consider that Dun and Bradstreet are tied to Thomson).
I'd be interested to hear from other UK local search experts, you never know you could end up on the mother of all UK local search projects.