Corsa diesel cutting out?

right i have a 2000 corsa standard diesel that starts fine but once its running it keeps cutting out without warning. its not stuttering or chugging. there is no smell of oil or fuel burning and starts every time. it is also fine on tick over. it also did not like it in the rain and was a lot worse than the first time it started doing it. apart from that nothing seems to be wrong with it so don't know what it could be. any ideas?????????