I'd largely agree with what's been said here -- food in the UK is actually pretty affordable and good quality (I loves me some Waitrose and M&S...) although eating out costs more (I particularly miss Mexican places with enormous chimichanga platters for about $6 and all the free chips and salsa you can eat.)
In general my wife and I have felt much more pinched financially since moving to the UK. The main thing is property -- we lived in Urbana, IL (a lovely midwestern college town about which I cannot say enough nice things) where the cost of property was nice and low and where a university job could net you a very decent salary, along with health benefits, etc. The main difference for us has been not so much the higer prices in the UK but the lower salaries: we're both in jobs here where we're earning about the top whack (given our qualifications and experience) and yet we're mainly scraping by without being able to save much or consider the prospect of owning a house. In Illinois, by contrast, we were both earning at or near the peak of our potential, and living much more comfortably, socking away savings, and generally not stressing about money.
Cost is only one of the factors, of course, and there are things about where we live now (E. Sussex) that I know I would miss if we went back.