The dinner at lunch time, and calling the evening meal tea is very much a northern thing.
When I was a kid
Breakfast
Dinner
Tea
Supper - usually cereal.
No
Breakfast
Lunch
Tea (sometimes call it dinner) DW even calls it tea now!
Supper
Don't always have any supper, just occasionally a bowl of cereal at about 10pm-10:30pm if a bit peckish. Or some toast.
dinner is the main meal to me, not a specified time, although at work would still say it's "dinner hour"
What's all this about dessert being supper? Dessert, if you have it, is directly after your main meal, it's pudding, sweet. It could be some strawberries and cream, ice cream, rice pudding etc.