I have a damaged grey leather electric heated drivers seat. I am not sure whether both driver and front passenger seats are identical since I could buy a used one of either if they are. Please help. I live in the South of the UK

 

Welcome to the forum Robert.
Are you saying the seat heater doesn't work? If so, try checking the seat heater switch first. I think you can swap it with the passenger switch.
Also check fuse F15 in the passenger fuse box.

 

The seat bottom cushions are interchangeable from side to side. I don't recall whether or not the full seat is interchangeable, but in any case you don't need to swap the whole seat.

 

Correct.

Seat cushion and seat cushion leather are interchangeable on the front seats
Also headrests - interchange from side to side.
Technically so will the seat back leathers, however you will have an awful hole from the movable armrest and no mounting bits for it on the other (non hole) side, you will have to remove it, so I've never attempted.