pretty sure there are 2 types of 'middle' rear seats, wagon and van are different. my mates MQ wagon (7 seats + tailgate) rear seats were ~70-30 split. i think van (5 seats + barn doors) might be 50-50, maybe fold down?
The van had a single piece middle seat that folded over into behind front row the same as the series 3 Landrover wagon did.
I would be interested if anyones knows the answer to the question as well as I am thinking about upgrading mine in the near future, middle and back row.