Thank you for the welcome and the reply.
My TV has a freesat tuner and has BBC iPlayer but no other on-demand. I have done some more tests and I think it is probably down to the transmission of the particular programme rather than the TV or the box. When trying the programme through The TV iPlayer the side black bands are there on the same programme but not so wide.
Just need to sort out the clunky remote.
My only other comment so far is the slow boot up from standby. Not anywhere near as quick as my Humax Freeview PVR.