Many students will choose to study abroad in London or other parts of the UK because they assume they will not have to be concerned with any language barriers. This assumption is somewhat false. Although the native tongue in the UK is English, there are many different slang terms used commonly that differ from what we use to describe people, places, or things.
English Football, not American Football like the NFL.
Most are familiar with the fact that football in America, and football in England are two completely different sports. English football is American soccer, and the closest thing they have to American football is rugby. This is just one of the many words which are changed in meaning.
English Fish and Chips with a side of Cider = American Fried Fish and French Fries with Hard Apple Cider.
Going out to eat? Well just be prepared that when you get your fish and chips, chips are french fries, not potato chips. If you want potato chips, then order some crisps. Also if you ask for an order of biscuits, you'll get a dessert, not an appetizer. Biscuits are not those savory buttered rolls served popularly in the American South, but cookies in England. If you order cider as a drink, expect it to be hard cider with alcohol, not apple cider served around Christmas in America; don't even try to order it hot.
When going shopping, remember to ask where the trousers are or to compliment someone on their new trousers. If you tell someone, "Nice pants," or ask for the pant section, you'll be talking about what American's refer to as underwear...that could get embarrassing. Another one to remember is if you say you'll get something stuck in your braces, in England that means in a pair of suspenders.
Now to get to the big ones to remember, such as in England if you need to find somewhere to pee, say you need to go the loo or the toilet, not the bathroom. A bathroom is where you'd wash up and bathe. If you're in the apartment and you door knob breaks, don't go around saying you have to adjust the knob because in England a knob is a penis. Finally, another good thing to not say in public is, "I fell on my fanny." It may be something you heard Grandma say in America, but in England a fanny is not a butt. Everyone can go look up what that is on their own time.
Overall, be careful what you say in England. You may assume that you think you know everything about the English language, but you only know everything about the Americanized English language. In the UK, there are so many slang terms, therefore it would be good to know what you're asking for. It will make for a safe trip, a good time, less language barriers, and no communication mixups.