Megane II Dynamique Convertible Starting Problem

My son's 55 plate convertible has started playing up. He has just returned from Edinburgh to Liverpool, and stopped a few times for fuel/tea/pee etc. On trying to start the car each time all he got was a clicking noise from the starter, and I told him to leave it for 20 minutes. This worked, and he got home OK.



What is likely to be the problem? He is a novice at cars, and I am not close enough to do anything myself at the moment, so what should be on his check list?



Your help is appreciated.



Thanks,



Mike