Less well-off people in the UK don't use the word dinner much to mean anything other than lunch. MphRedux is right about the way they use the word tea, particularly in the North of England. It may be changing now, but the usage was very common twenty years ago.I usually consider high tea to be a very high-end gathering where tea is served. I wouldn't use the term in place of the word dinner.
this is exactly what I meant!In New Zealand, people say 'tea' quite regularly. They say 'dinner' as well.
The first time I heard that expression was when a New Zealander friend asked me whether she could be at my house for tea. I said "Yes, sure!, what time are you coming over?'. She replied 'What about 6?', and I said 'great'.
When she arrived I had already had my dinner and had only black tea and biscuits prepared for her. Back then I wondered why she ate a lot of biscuits!!! (she was hungry of course)