Hi Mark,
Plenty of imports in the UK. Mine is a JDM import and I've kept the speedo in KPH, no problems with MOTs as they'll record it in Km.
You're right the car will likely need to be waxoyled to protect from rust. Can be a DIY job, or a few hundred to have a specialist treat for you.
I doubt heating will be an issue as this comes from the engine, quick way to check is turn it up and see if it gets even hotter in there!
Next step is to get prices for shipping including transportation insurance. Once back in the UK you'll have to sort registration with the DVLA, road tax, and finally get it an MOT then you're good to go.
Best of luck with the move,
Ben