What, no McVitie's?

Actually, I've never seen anything quite like an American biscuit in Britain. The closest equivalent would probably be a scone or Irish soda bread. The important distinction is that it's made without yeast.

Biscuits are primarily served at breakfast. (That is, if biscuits are part of the local culture. Biscuits are uncommon in Minnesota where I live now; they are much more common in the South.)

It seems to be a universal custom that breakfast consists of food that can be prepared quickly. Compared to bread, biscuits were quicker because you didn't have to wait for the yeast to rise. Waffles and pancakes were another quick way to prepare a bread-like food. Toast is customary at breakfast because it is really yesterday's bread reheated.

When I was a kid, visiting aunts and uncles on their farms in Kentucky and Arkansas, breakfast was served with biscuits fresh from the oven. (I doubt that they had biscuits every day; I suspect they were working extra-hard to be hospitable.) In those days, in those places, bread was something you bought at the store; biscuits were something you made at home.

Garrison Keillor, on his Prairie Home Companion radio show, used to have fake commercials for a fictional product called "Powdermilk Biscuits." He'd say, "Buy 'em ready-made in the brown bag with the dark stains that indicate freshness." In real life, I've never heard of anyone selling biscuits this way. It sounds like an unpromising business plan. Ideally, biscuits should be eaten immediately as they come out of the oven, as soon as they are cool enough to touch, while they are still warm enough to melt the butter you put on them. They quickly lose their appeal. You might be able to induce a kid to eat a cold biscuit if you put enough jelly (or jam) on it. Day-old biscuits are awful.

Here's a "from scratch" recipe for biscuits.

There are various ways of buying some of the ingredients already mixed, to save you a bit of trouble, e.g. Bisquick.

You can also buy the dough ready to cook, in a refrigerated can.

You can even buy biscuits already cooked and frozen, but it sounds like an abomination to me.