Paul,
Having now seen that all the controls for your seats are on the seat base itself, then the connections should be a lot simpler than I'd feared.
There is likely to be an ignition switched main supply and ground return to the seat and quite likely to and additional keep alive permanent supply to the seat memory in rather the same way as most radios would use.
A wiring diagram from the donor car should give all the clues needed.
There could still be the issue of the pre-tensioners or your seat might not even have them. There is still likely to be an occupancy switch especially on the passenger seat and simply on off switching to show the seat belt has been engaged. You might choose to ignore these or the MOT tester might insist that any warning light is functional.
Bob