"I have seen that some have put insulating padding at the rear. I am assuming that it is on the inside? does it effect the putting of the seats back?"
With seats out Dynamat sound deadening on bulkhead & under the seats, some also do the transmission tunnel & side panels. Aluminium tape to seal the gaps between bulkhead & body. It should not affect refitting the seats with one layer. I cannot say if the tape alone will reduce the noise much but will reduce the dust ingress.
http://www.talkmorgan.com/ubbthreads.php/topics/176831/1
