I would say it's a rural item. Plenty of farming households across the British and Irish isles would have them. Not all farmers are not wealthy nor come from old money.

You would throw wet laundry on top of them either and overnight they would dry. They have multiple purposes but ultimately a source of heat that is effcient for long grey wet winters presented by the Atlantic temperate climate.

Yes, indeed. In my (at the time) sister-in-law's 17th c. two-up two-down stone cottage an oil-fired Aga was, in fact, the sensible choice. Not to say running it wasn't costly, but electric heat would have been far more expensive. It was also lovely to cook with. Put the drying rack in front of it, and clothes dried so thoroughly they didn't mildew after you put them away; also, you could throw your shoes into the low oven before you went out (amazing!), and again after you came in to get them dry.

My then-partner and I lived in an even older house, whose only sources of heat were a defective boiler and a coal-burning grate in the (genuinely medieval) fireplace in the living room. Our experience was, shall we say, authentic to the time-period in which it was built.

People underestimate how miserable the British climate is in winter, and how energy-intensive those old homes are to heat. An Aga wasn't invented as a status symbol, but as a practical item for a particular circumstance. Moving it outside of its original context is what changes its meaning.