dveitch: Thanks to you all.
The suggestion that I pull the HDMI plug to separate recorder and TV has the same effect but I can do this my way from my armchair. If the aerial feed is from the wall to the recorder and then on from Recorder to the TV this does not work as the recorder does control that RF Out signal. Turning off the Panasonic Viera connection certainly stops the Recorder from being visible on the TV but does not, by itself, allow other channels to be viewed on the TV while two channels are being recorded and signal input is still through the Recorder.ick
Now get into the Recorder setup menu and find RF Out and Viera Link.
Viera link should be uner Connection. I see you've turn Viera Link off so you don't get any HDMI control to the TV. One problem solved. Mine used to switch the TV to HDMI in from the recorder as soon as I turned on the recorder until I turne this off.
RF Out should be found under Others in the menu. Turn this on. TV will then get antenna signal all the time with recorder on or off but probably not if the recorder is unplugged from the mains. Haven't tried. This should solve your remaining problem. Interestingly my previous model Panasonic had it on all the time, no setting to turn on/off.
Alternatively stick with the antenna splitter.