I had a Disco 1 electric seat in my 90 for a very short while as, like Mike, I found the driving position uncomfortable. I was too close to the wheel both horizontally and vertically as the seats are both taller and longer than a standard defender. I probably could have moved the seat back further if I had removed the bulkhead behind the seats (but I don't want to) but there is very little that can be done about the height of the seat-base and even fitting a smaller after-market steering wheel did not help. I to am not exactly tall at 5ft11.
I fitted a Britpart replacement seat (as I didn't have the original) like this :- click me and have so far found it to well made and comfortable, plus it retains the ability to remove the seat base.
Pete.