There is a similar site that lets you add your own foods and calorie info (which means you can add in UK foods) at http://www.my-calorie-counter.com/.
FYI, you can add in your own custom foods to Sparkpeople, too, and it's always free!
I'm a huge fan of Sparkpeople - over the course of 9 months last year I lost 46 pounds, 6 inches off my waist, and went from a UK 18 to a 12 (US 16-8). And I'm here, nearly 9 months after reaching my goal and I'm still the same size and actually even fitter than I was then.
That site is fantastic for changing your entire lifestyle, not just going on some "diet". I haven't even logged back into the site for about 6 months, just because I know how to maintain on my own now, from all the things it taught me last year.
Oh, and here's before & after photo to motivate you guys.