Gazza, the jump seat (or the imaginatively named 6th seat as it was better known!) is just the same as the 3 rear crew seats. It lives on a track between and behind the 2 pilots' seats,
Just looking through my pics for you. Firstly, the entrance step someone mentioned:
Main IP's
Rear IP's
As to the seats, I appear to have studiously avoided getting them in my shots it seems!
Back of the 6th seat, taken during a taxy run so not the best pic
If you like, there is a rear crew seat in the garage I can photograph for you.