I once worked with an English bloke called Ben and when he called his mid day meal "dinner" I was quite perplexed as that term, as for me at that time I thought it solely referred to an evening meal. When I asked him why he called lunch dinner he said that where he came from (which sadly I can't remember, though he'd spent most of his adult life in London) dinner is the main meal of the day, regardless of whether it's taken around noon, or in mid- or late evening. He didn't mention any class distinctions but perhaps he intentionally avoided the issue or thought me too foreign to understand.
Sorry, I just killed a few hours reading this old thread and boy did they fly by.
I'd love to discuss the original subject too at some point.