Как будет на британском 8:15,9:15,12:25,11:35,3:00,4:50,5:10.

8:15 Its quarter past eight. Или: Its eight fifteen.
9:15 Its quarter past nine.
12:25 Its twenty-five past twelve. Либо: Its twelve twenty-five.
11:35 Its twenty-five to twelve. Либо: Its eleven thirty-five.
3:00 Its three oclock.
4:50 Its ten to five.
5:10 Its ten past five.