Having lived in the U.K. for over a year now, I thought I'd share with you some "bits and bobs" of British English...
Hiya = Hello
You Alright? (like there's something wrong) = How are you?
Peckish = Hungry
Poorly = Sick
Aubergine = Eggplant to us Americans
Nappie = Diapers
Brolly = Umbrella
Tellie = Television
Biscuit = Cookies in the States
Chips = Fries
Crisp = Potato Chips
Gherkin = Yes, as in the Gherkin means pickle
Pudding = Dessert
Pants = Underwear not to be confused with Trousers which means pants, Americans
Suspenders = no, not that kind. It means lingerie or garder belt.
Braces = suspenders in the UK
Jumper = Sweater
Boot = Trunk of a car
Bloke = Guy as "that's a nice looking bloke (read: guy)"
Mate = Friend
Brum = people from Birmingham, also called Brummy
Drinkie-poos = drinks
Pressie = Presents as in "I got a birthday pressie for you..."
Chav = derogatory for someone of the underclass
Mum = Mom in the U.S.
Yank = us, we Americans!
Quid = Buck, "That will be 10 bucks/quid"
Fancy Dress = Halloween Costumes
Serviette = Napkins
Boot = Trunk of the car
Bonnet = The Hood of the car
That's all for now. Hopefully more to come!