I grew up in as working-class an area as you can get, and the evening meal was always called tea. During the day we'd have breakfast - lunch - tea - supper (just before going to bed, it'd be toast or cereal). As I've moved further South though, I've noticed that 'tea' has become 'dinner', and now I'm in London I think I'm the only person I know who calls it tea. BTW, the actual drink tea is not involved with this in any way! Everybody here knows what I mean when I say tea rather than dinner though, so it's not an unusual term.
The only time we* have afternoon tea is on the weekend, when all meal times are shifted about a bit. Have a late breakfast, then find a teashop by mid-afternoon and settle in for the next few hours with a pot of proper tea and a 3-tier stand full of little cakes. Then maybe something else to eat about 9pm, but usually not a full meal.
The only time I've ever seen or heard of High Tea is in an Enid Blyton book, which I think had a farming family and this was their main meal of the day once everyone had come in from the fields.
A tea-break on the other hand, does involve the drink tea. Usually a couple of times a day when at work, about 11am and 3pm, when everyone descends on the kettle.
*By 'we' I mean my friends and I, not everyone in the UK