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Well I think I now know what the problem is. The TV still thinks it's being operated by a sky remote, rather than its own. It's right, it is, regardless of a connection or not to a sky box.
I can get the TV to go to standby using the sky remote, which doesn't help but does go to show that it's not the TV remote that's faulty, rather it's been made redundant by the sky remote.
So the TV remote still won't work, so now I need to find out how to unpair the TV from the sky remote, without impinging on the sky remote's ability to work the sky box. As it goes, there are all the BBC channels there without re-tuning the TV. As we don't watch an awful lot of TV upstairs, and no grand-children are coming over currently, we have plenty of time to try and get it sorted.
As far as the channels available without a subscription go, there is definitely a rapidly increasing shortage of anything worthwhile to watch. I could get a firestick for it I guess as we have a netflix subscription courtesy of one of the grandchildren. But that would only be something else to try to figure out how to work!!