Great News ! ARC all works perfectly.
The setting you mentioned was what I needed however it was not in Menu page as expected.
Instead I tapped the
-> green Viera Tools button my remote
-> selected Viera Link
-> then the speaker selection menu appeared where as you stated I chose Home Cinema.
What's also great now is the volume on panasonic tv remote also controls the amp volume.
The only minor issue I have is when I switch tv off then on again it automatically goes to av4 (my ARC input) so I have to tap whatever it was I was originally playing I.e net radio.
Nevertheless I'm very happy it works close to perfection. Thanks all!!!