Just thought I'd bump this with some more news - there's been some great analysis done by a guy on Reddit:
https://www.reddit.com/r/teslamotor...easibility_study_on_the_old_model_3_modified/
Short version: It appears possible to jerry rig a heated steering wheel to get power on older Model 3s. It blows the e-fuse (presumably because it's expecting the wheel to use that much current). That sounds really bad, but it's progress
It also appears that Tesla may have steathily changed the steering wheel harness (1112053-00-D) to have an extra blue connector for the heating element, per that linked thread. Annoyingly this means whilst I thought the steering wheel itself was the only thing that has changed, it actually might not be. It seems that Tesla might be modifying components without changing the SKU - boo!
Also - from
this post it appears as if it might be the case that the "non heated" steering wheel (part: 1095222-90-O) that I thought
wasn't heated, because the UK EPC shows a different SKU for the heated MIC one (1490214-CN-B) - per
here - might be wrong too. It seems to be the case that Tesla are just calling the standard wheel with built in heating element "
M3 - SW ASSY, PUR" even though it has a heated element in, because that's what is going to be standard.
The good news is that anyone wanting to retrofit a heated steering wheel would need to buy the whole steering wheel, which as an assembly contains the required harness and software controller anyway, so ultimately I think the retrofit job ought to be as simple as taking one wheel off and putting another one, and getting a service centre/Tesla to unlock the option for the car.
I would expect a replacement steering wheel to cost a minimum of £500, though, plus the option cost.