Here in the souf of Ingerland, it depends on the generation you ask. I think most younger people will say the three main meals are breakfast, lunch and dinner (dinner being late afternoon/early evening).
My grandparents (born in the south and have always lived here) say breakfast, dinner and tea (dinner being early afternoon), which is how most people oop norf still say it. So it seems that the widespread adoption of B-L-D is a fairly recent thing in the South, I guess due to the influence of London and the growth of the middle class.