I'm British and like many Brits I've visited a few. My list is incredibly varied, having lived abroad a few times, backpacked and been on a few business trips, so it's quite a lot.
But from memory the US, Mexico, France, Belgium, Spain, Germany, Italy, Nigeria, Ivory Coast, Togo, Ghana, Greece, Sweden, Hong Kong, China, Singapore, Malaysia, Vietnam, Austria, Australia, Hungary, Cambodia, Thailand, Ireland, Japan, Bahamas... There might be one or two more but I can't remember at the moment.