Overnight disposible nappies

[Debbiethemum]

Our 3 yr old ds is recently potty trained and is getting very good at it with very few accidents, however he does seem to be really filling up his overnight nappy. Does anyone have any reccomendations for a really absorbant (sp) nappy for use at night, otherwise he leaks through to his sheet/duvet.
Thanks

We use pull-ups for our ds at night and call them his night time pants to get away from the idea o nappies. It seems that because he sees them as pants he keeps them dry 90% of the time and in case of any accidents we bought a waterproof sheet from aldi (which I'm very impressed with and a bargain at £9).