Okay so when you come to visit there a few things you should know about British restaurants.
First many of your favorite fast food joints are already out there so if your homesick you can get your BigMac fix. You have heard that the Brits call French Fries "Chips" The younger generation calls them fries just like us so don't worry about it. You will want to double check your favorite number. A number 10 my not be a number 10 in a British fast food place. Other then that they are the same and taste the same. KFC on the other hand does not have mashed potatoes.
Of course you did not travel all this way to pay twice the price for American fast food. If you decide to go to a real restaurant here are some tips. You don't normally tip the waitress. You also don't usually tip a bartender. Since you are not tipping they don't care about the quality of your service, so expect the worst service you have ever had.
When the waitress first comes over they will ask if you want still or sparkling water. Still is like bottled water and sparkling is with the bubbles. If you ask for still water they bring out a glass bottle of water. You may need to ask for more if you run out. They don't always automatically bring more.
The portions are much smaller. I went to a run of the mill British restaurant and ordered a steak. It was 6oz. Not 16 it was 6oz. That is about the size of a deck of cards. As your eating you will notice they don't come by to check on how you are doing or to bring you your check. When you want the check you need to ask for it.
If you manage to have enough left over to bring home don't. It is considered rude to ask for a doggy bag. honestly I could care less about offending a restaurant. I paid for it so I should get to bring it home.
If you decide to order take out like pizza or Chinese they call it take away.
Food terms
Bangers and Mash = Sausage and mashed potatoes
Rockets = a type of lettuce that has pointed ends
zucchini = courgettes
lima bean = butter bean
Eggplant = Aubergine
Scary British Food
Black Pudding is made from blood
Marmite is a spread made from the leftover yeast from brewing.
Toad in the Hole is sausages covered in batter and roasted.
Bubble & Squeak is like leftovers that have been fried in a pan.
Pie and Mash used to made with eels
Need I say more?