Turn both your TV and set-top box on then disconnect the TV from the mains supply at the wall socket, does the box remain on?
apologies for not responding sooner, had to work.
so grateful for everyone’s input and help, it’s been invaluable, but the good news is I think..... I’m certain I’ve sorted it.
I tried everything everyone suggested and it didn’t work, so before taking the main TV off the wall I got a spare SONY Bravia tv and plugged that in and connected the BT Box directly into that, so no hdmi to the main tv or the Sony surround sound..... nothing happened the box didn’t even turn on!
After much head scratching turned the main tv on by mistake and the BT box came to life, this really puzzled me, as the picture was on the second tv!? Turned the main tv off and the BT box went off, the air was a little blue.
So the only common denominator was the anti-surge extension sockets that the tv, surround sound and BT box was connected to, so unplugged everything, used a standard extension and plugged the spare tv into that and BT box switched on - got picture and sound, turned tv off and BT box stayed on! Tried it with main tv and same result, BT box stayed on.
So problem seems to be sorted. Attached is the extension lead it was plugged into, clearly something in that device was causing an issue.
thanks again everyone, I’m not a tech expert, but I’m usually good with stuff like this, it was beginning to get on my wick, especially when things turned off and on that weren’t physically connected or so I thought.
thanks again everyone
I wish you'd mentioned a surge protector earlier, we could have had it sorted in no time. C'est la Vie