Waking before 6

My LG has started waking before 6 and it's driving me crazy, she started doing it before the clocks went forward so it's not that Iv tried capping naps & letting her nap as long as she needs She is currently sleeping in a long sleeve vest and a 2.5 tog sleep bag, room is 20 Has anyone else had to change anything to stop them waking early that has worked?