Well, say that this is filling in until the experts arrive, but as a sort of rule, if the plugs and sockets are the same and fit, it should be the same.
Having put Mk 2 electric seats into a MK 1 and owned several MK 1's with them fitted from new, as far as I'm aware the electrical supply connectors will be the same for the electric adjustment of the seats. Bear in mind however that MK 2 seats also have integral airbags, hence the loss of width adjustment on them. All you need to do is just leave them disconnected (they are the thin orange wires).
The rear seats have a different shape around the seatbelt clips. On MK 1's the clips are located in a cut out in the seat, on MK 2 they are on a strap above the seat. Also the centre belt on MK 2's is a static belt rather than an inertia, so if you are putting in MK 2 rear seats make sure you also get the belts as they are not compatable.
I prefer the Leather electric on the Mk1 to the Mk2 ... better shape, adjustable side cushions and in the rear, the head restraints are lower profile to the front in the Mk1 which makes a big difference to visibility thro' the rear window.
