Any Z3 or 4 is worth significantly more in Australia. I have considered buying another from the UK and shipping it, It would still be viable, corrosion seems to be an issue in the UK, mileage an issue here. "Just down the road" in Australia has a very different meaning in the UK... I very nearly convinced my wife that buying @gookah 's one was a good idea..Yes I read that too. I'm surprised at their assertion that Z3M cars are dearer than Z4Ms are. The Z3M Coupé is certainly prized in good condition, but why not the equivalent Z4M Coupé? My son has the latter and he's modified the suspension and brakes to allow high speed track usage, sipped it to New South Wales where he now lives. Apparently the rarity in Australia makes it worth a bomb!
I'll do a bit of research on prices here for 3s and 4s.
Most are for sure such as bushes, shocks etc which require replacement as much for age as well as mileage. A high mileage M of any type just needs more fettling from my experience. We know that any M5x engine will be bullet proof, M4x likely will need a head gasket, but S54's have bearing shell issues - and those now tend to be classed as an every 80k service item. Probably be fine without changing them (mine were starting to wear at 123k) but spinning one probably means a new engine at £9-10k.most of the "upgrades" involve service parts