Regarding meals:
"Breakfast" appears to be universal in the UK. No arguments there.
The second meal of the day may be referred to as lunch or dinner, depending on what part of the country you're from.
The third meal of the day may be referred to as dinner or tea. Again, this depends on where you're from.
The fourth and optional snack before bedtime is referred to as supper. I have never heard it referred to as anything else, but, again, this may depend on where you're from.
Personally, I say breakfast, lunch, and tea.
A lot of foreigners do not know that a lot of Brits refer to our evening meal as "tea," and since they have a mistaken stereotype that we all drink tea all day long, they often get things mixed up. "Do you want to come over for tea?" may not mean sitting politely in someone's living room sipping a beverage out of a cup and saucer. It may well be an invitation to dine. 