whilst I was looking up something else I came across this site, ' livestrong' which is a website owned by the lance armstrong foundation. (edit: it is the commercial arm rather than the charity) It has a lot of info on diet and what seems to be a very good daily calorie/macronutrient /exercise calculator/
I've found other versions of this elsewhere but this one has the advantage that other people can input foods to the database. It seems to have had a fair amount of UK usage aand there are a lot of foods from Tescos, Somerfields etc . (caveat : you need to check that the figures at least look as if they've been corrrectly input)
It has a nice feature in that you can save regular meals and also a pi chart with protein/carb/fat percentages for the day. You have to register (and as far as I can see there is no payment involved) to save your data but you can play with it without registering
I'm not sure that I'd keep it up for a long time but it seems a good way of doing a food journal for a week or two.