Thanks for your quick reply. I searched a little deeper and under an options menu there IS an option for "extended surround" . Changed this from "Auto" to PLIIx and all fixed.
Well here's my first post...
I've been using a Yamaha RX-A1000 receiver through my 7.1 speaker set up for a few months at home and generally I'm very happy with it, with one exception...
My old Denon AVR-3805 had a feature where a 5.1 source (eg dolby digital or DTS) it could output to the rear...