Hopefully, you willl have a rented apartment/cottage for at least some of your stay and can cook some of your own meals. Supermarket food in Britain is also more expensive than in the US, but it's still much, much cheaper than dining out. Since most pub food is not a complex culinary delight (apart from some "gastropubs," which are generally quite expensive), we found we could largely duplicate the "British food" experience ourselves. We would often buy "pot pies" in a bakery (things like "steak and stilton pie") and easily warm them up with a minimal of fuss.