I wish I knew more about the UK market, because I did wonder about this one earlier. I want to know three things:
1. Where does .com stand as a tld in the UK market?
2. If they like .com's, how well do they like "*UK*" .com's?
3. How well do they like the term "phone" in the UK compared to the alternatives?
If you've scored three goals for the questions above, then as far as I'm concerned you're looking at a domain that would be worth a lot, easily xx,xxx to xxx,xxx.
Problem for me is that I just don't know, so I'd be more interested in some credible testimony from those who really do.