Thought it might be worth addressing the original question.
We (Paul Harwood and myself) once tried to start a UK Marchex, back in the days when we owned Streamic. I had a meeting with three investors with a £5m fund to kick things off. I outlined the opportunity and everyone seemed totally interested. Unfortunately nothing transpired due to some shareholder issues at the company, boring internal goings on. Indigestion.
This was "back in the day" when high traffic, "sensitive" domains generated significant chunks of revenue, which they still do I guess... but the risk of owning such names was relatively less severe. Focusing on the UK market exclusively for this business model would have actually been pointless anyway. There are some good UK domain names like this, but .com usually gets at least 8 times more traffic for the same keywords. This means that Marchex can happily get away with buying GENERIC domains (for multiples based on PPC revenue), but a UK-orientated Marchex really couldn't work on the same basis at all. The latter would absolutely have to rely on typos 100%
So, the business would have actually been a Marchex clone, more or less. It would certainly not have been a UK version of Marchex, as that would have been to pointlessly ignore the true size of the opportunity. Equally pointless to buy up large quantities of amazing one word generics for the typical prices commanded by UK domainers *unless those generics get SIGNIFICANT traffic. It's just way, way too hard to predict things on a development model. I can't see any investors being interested in that really, unless you managed to impress them with flowery language.
I do like a good domain name. They are memorable, they smack of authority and they can open up opportunities in the right hands. There is also no doubt that a generic domain can benefit you in the search engines TODAY (this could so easily change though!)
In general I think many UK domainers would do themselves no harm by stepping things up a gear to develop something worthwhile. Purely focusing on buying and selling names and/or domain parking is not only lazy, but takes a lot of luck, guts and money, and these days probably all three in healthy measure. Example: If you've got the guts and the money to buy mortgage.co.uk for £200k then yes, you might just sell it for £1m in five years' time, if you're lucky. But you can't predict that. It's just as likely in my view that such .co.uk domain names (no matter how fantastic we think they are today) will eventually be perceived as worthless. Totally possible.
If you're convinced that buying and selling domains is a great business model, then by all means, ride that wave while it's there. But at least focus on the absolutely premium, best of the best domains. In the current environment you're never going to get rich dealing in "almost great" domains for moderate sales prices. In my opinion most end users and the business world in general already does "get it" when it comes to generic domains.
I agree with Sean's comments in this thread.