I remember a discussion on this a while ago and Rhubarb Commando having a good reply. Dinner in Britain was traditionally the main meal, served in the middle of the day in working class homes - in the days when it was possible to go home in the middle of the day and in the evening in upper class homes. As a child I would always call the midday meal dinner and the evening meal "tea". Supper would have been a light meal, such as toast, served before bedtime.

These days I'd tend to use lunch, dinner and supper much as Wordy describes.


[Edit]Here's a link to an earlier discussion: http://wordsmith.org/board/showthreaded.pl?Cat=&Board=words&Number=8454