Hi. I fitted E46 M3 seats to replace my original heated electric memory seats (non-M), so the Z4 heated memory seats are available. I had to swap the pre-tensioners over from the Z4 seats onto the M3 seats as well as the passenger occupancy sensor as these had been removed from the M3 seats.
Seats worked fine when they came out. Condition is good (as opposed to vgc/mint). Only downside really is that the passenger seat back used to pop off every now and then. Some attention to the clip arrangement should resolve that I think. Happy to post pics if you're interested. I'd take £125 for them because of the missing parts. Based in Somerset.