Great looking site, Charlotte is right, though.
If you are after the low end of the market, I would suggest that your idea of a second domain is a good one. Assuming your deals are good, that front page would hit you with the £ and click straight through to a "buy". No reason why you can't declare the association, and have a click through from one site to the other, but I suspect that there are two completely different types of customers.
Not the end of the world, and probably something to worry about after you've stabilised the site for whichever you perceive as the core business.