Thanks rum, much appreciated. I've done a fair bit of retrofitting on Audi's and VW's in the past, so I'm confident with getting my hands dirty and wallet emptied 🥲
Unfortunately I failed to find much info via Google either. Lots of people swapping them into 5J/mk2's, but couldn't really find anything beyond people mentioning they'd done it on NJ/mk3's, with little more information included. Good to know about the loom, tbh I forgot Kufatec include instructions!
Perhaps I'll have a look for some Monte Carlo seats, it seems those are much more commonly heated. Should be a nice comfort upgrade for her as well, hers is an SE with, afaik, the most basic seats available on the model.
As well as the loom and heated seats, Kufatec suggests I'll need "Original seat heating controller" and "Original control unit for seat heating".
I suppose one of these is the replacement buttons unit, including the two additional buttons to control the heating function for each seat. Struggling to find much info on this, or even a P/N. Might be time to fire up my ETKA VM and do some digging.
Update: Checked ETKA. Seems this is P/N 6V0927132B or 6V0927132C. B supports PRs 4UC and 4UE, "driver airbag" and "airbag for driver and front passenger" respectively. C supports PR 4UF, "driver and front passenger airbag with front passenger airbag deactivation". I'll have to check which one she currently has.
I'm then assuming that the other is the relay, which seems to carry P/N 6R0959772E.
If I go ahead with the project, I'll be sure to write up a guide for anyone else!