This afternoon I looked into the noise levels which have been gradually increasing across the middle, and sometimes across the top of the medium wave band here. My Sky router has never been a problem regarding interference in the past, but I thought I should re-check it and switch it off to see if noise levels reduced. They did! So my trusty and noiseless Sky router is now causing QRN.
I wonder what has changed? It's almost three years old. I can only guess that some components are beginning to break down. Perhaps I should make it go 'pop' and call the engineers.
Of course, I simply assumed it had a 240v input.