You can get a kettle for £30 now with temp control, albeit you choose from 4 temps - 40/60/80/100 (low-mid range, low prices are around £12; mid would be £30-50 IMO): eg https://amzn.to/2Us6fPP [aff].

Strangely all UK stores (Tesco, John-Lewis, Currys, et al.) appear only to sell the traditional boil-only ones, which is curious.

As I drink primarily instant coffee I'm in the market for a temp control kettle, hopefully with double-wall insulation. Open to suggestions!

I found a decent one on Amazon that has a thermometer - so you can hit any temps you want to, at the cost of having to watch it (worst case you dilute with a bit of cold water if you overshoot). Very noisy though (Klarstein)

I purchased one with a temp setting, they exist and are amazing.

This is the one we have at home https://www.breville.com/au/en/products/tea/bke720.html, works great!

Normal electric kettle does not work by sensing the temperature, but by detecting change of pressure inside caused by the boiling water. The mechanism is purely mechanical, simple, cheap and reliable but there is no way to make the temperature configurable.