Tea with no sugar is like 20 calories with milk, add 35 for each sugar you have (roughly). So for say, three cups of tea with a sugar, probably 150-180Kcals
A simple sandwich (2 pieces of regular bread with filling) will be between 350Kcal (for say, just cheese and light mayo), up to 650Kcal (for say sausage, bacon and egg mix).
Most desserts are just sugar so either choose natural sugars (fruit) or skip. A slice of cheesecake is going to be between 350Kcal-650Kcal, depending on size etc. A fruitbowl will probably fill you more and be about 150Kcals and a teaspoon of peanut butter at 25Kcals
Scones and clotted cream is basically sugar and fat so that's gonna cost you prob 250Kc per scone and then just budget 100Kcals per tablespoon.
It;s not an exact science but I'd say
2 cups of tea with a sugar, a scone with cream, a chicken/bacon and mayo sandwich finished with a slice of cheesecake is gonna set you back about 1,300Kcals