Britain isn’t terribly big, and as such, you can get around the island and see some other stuff. If it’s the first time you’re visiting, look into London day trips that takes you to Stonehenge, Windsor Castle and Bath. These are some of London’s most famous landmarks, and each represents a period of England’s distant past. You’ll regret not going, and the guides generally make the trip informative and amusing. These can be found for under $100 a person, and they’re a good bargain.
Another castle day trip package takes you to Oxford, Stratford on Avon and Warwick castle, which has a Madam Tussaud’s Waxworks as well as a “spooky” dungeon. The castle gardens are beautiful, and so are Oxford and Stratford on Avon.
You can also get a Eurostar pass to visit Paris. These are pricier (from $245, usually), but you can get them independent or escorted, and they give you a day to explore the City of Lights.