Electronics such as heated seats, movement (on driver's seat) etc works fine too and is not too hard to do.
Here's the donor car:

A friend mechanic welded them in for me, using a combination of the old rails/metal bits from the stock MX-3 seats along with RX-8 seats. No welding or modifying of the car itself or anything crazy like that. It took him about 4-5 hours to do this from start to finish without much previous experience of welding seats.
The price in total was 200 for the seats and 150 for the welding. - 350 euro for one of the nicest mods you can do to your MX-3 (In my opinion). The headroom is reduced a little bit however.
If you need any help in regards to fitment or images of how the welds look, feel free to ask!
Anyway, here are comparison pics:
Before:

After:

