By 'Broadband Extender Flex', I actually meant the Broadband Extender Flex 500 which is part of the Wi-Fi Home Hotspot 500 Kit.
So, the arrangement I have in mind, is that the Home Hub 5's power supply would go into a socket extension lead like the one pictured above (with a laptop also plugged into it), and then the socket extension lead's plug would go into the Broadband Extender Flex 500's pass through socket, with the Broadband Extender Flex 500 plugged directly into the nearest wall socket.
Then upstairs, I would have the Wi-Fi Home Hotspot 500 in an unoccupied plug close to my desktop.
Would this arrangement be likely to work?
** Walks in and hammers up a "Please don't feed the trolls" sign on the virtual wall ** 😄