When Americans and Canadians visit England, it takes a bit of getting used to when you hear locals asking if you are also going to “Europe” on this trip. This might stem back from the Colonial days, when the sun never set on the British Empire, and England being part of Europe seemed like a quaint notion, but it’s still true that most Brits refer to the Continent as Europe, and only in the technical sense does that term apply to the UK.
With that in mind, it’s not a bad idea to visit somewhere else in Europe on your England trip. It’ll almost certainly be cheaper than you’d think to add in at least one other major city, and it also adds some really nice contrast to the England part of your trip.
With the possible exception of Dublin and Stockholm, most of England is just about as expensive as things get in Europe. Compared to London, Paris will feel cheap, and compared to Edinburgh, Barcelona is a real bargain.