Hi Karl,
I have today, factory reset the router and manually set the figures you gave me and then rebooted the Youview box.
I've rechecked all cables and both powerline adapters and reset these. They are both in their own wall sockets and on the same electrical circuit in separate rooms about 15 metres apart.
The TV engineer who called yesterday, swapped both powerlines and checked them and replaced the originals, as new ones made no difference. He checked the cables also and hooked up his tablet using the powerline adapters and the signal was excellent. He was unable to access the internet channels or the Bright Sparks channel either, which is when he phoned in to give his report.
The 3 previous BTopen reach engineers have tested the line from the exchange to the street cabinet and from there to my house and replaced all interior cabling and master sockets. None of the 3 engineers who have visited, could find any fault on the line or the broadband signal. The Youview box has been replaced as has the router (twice) and all new equipment was checked yesterday by the engineer.
Rosy B