I've been to the UK before, but only in short spurts. I am just wrapping up a month-long visit, and during my stay, I have compiled a list of differences between English and American speech. I've had quite a laugh over some of the uses and pronunciations, and so, without further ado...

English American

• Holiday vs Vacation
  
• Chips vs Fries
  
• Crisps vs Chips
  
• Garden vs Backyard
  
• Lorry vs Truck
  
• Trolly vs Cart (as in a shopping cart)
  
• Knickers/Pants vs Underwear
  
• Loo/Toilet vs Bathroom/Restroom
  
• Let vs Rent
  
• Biscuit vs Cookie
  
• Torch vs Flashlight
  
• Vitamin (pronounced with a soft "i" as in "big") vs Vitamin (pronounced with a hard "i", as in "bike")
  
• Drink Driving vs Drunk Driving
  
• Boot vs Trunk
  
• Nappy vs Diaper
  
• Swimming Costume vs Swimsuit
  
• Boots vs Shoes (specifically athletic)
  
• Cling Film vs Saran Wrap/Plastic Wrap
  
• Sun Cream vs Sunblock/Sunscreen
  
• Pupil vs Student
  
• Vest vs Undershirt (specifically the one with no sleeves, ala the "wifebeater" style)
  
• Queue (how many vowels can we put in succession in a word?) vs Line
  
• Fillet (ignore the French pronunciation and say it just like it is spelled: Fill-et) vs Filet (pronounce it like the French intended: Fil-lay)
  
• Jalapeño (ignore the Spanish pronunciation and say it just like it is spelled: Jal-a-pee-no) vs Jalapeño (pronounce it like the Spanish intended: Hal-a-pen-yo)
  

I'm sure there is more, so feel free to add to the list.