Have you looked at a map of Europe? England is an island. If you want to visit London, then fly there. Otherwise, you'll have to take the Chunnel to Paris, and then you've only made it as far as France.
Where do you want to visit? Most international airports have good flight deals to Paris and Amsterdam (and BIG hub for Europe, the middle east, and Africa). You may also get a decent deal to somewhere in Italy (like Rome), or maybe Munich. The airline websites let you search! Kayak also has a great 'explore' feature where you enter your home city, the month you'll travel, and then it'll give you flight estimates. It's a great feature when you don't know where you really want to go.