Perhaps consider removing the powerline ethernet connection between the router and Living Room Sonos One and then either wire a speaker (or Sonos Boost) direct to the router, or run the Sonos system on your routers WiFi signal instead. Powerline adapters can/do sometimes work, but are not an officially supported device by Sonos.

If you decide to opt for the wired setup, then also try to do the following (if practicable with your particular router):

• Set the routers 2.4ghz WiFi to a fixed ‘non-overlapping’ channel 1,6 or 11 and choose a 20MHz channel-width
• Set the SonosNet channel in the Sonos App “Settings/System/Network” so it is at least 5 channels away from your chosen router channel.
• Remove the WiFi credentials from the “Settings/System/Network/Manage Networks” in the App as those are not needed when running on SonosNet and it will stop your devices hopping between SonosNet and your WiFi signal.
• Ensure all Sonos products, particularly the wired one is at least 3 to 4 feet away from other Wireless devices including the router and other access points.
• This final suggestion is optional, but often worthwhile... Consider adding the Sonos IP addresses to the local routers DHCP reservation table, as that too will improve stability, particularly during updates and reboots of the local network.

The Sky Q router has a habit of trashing Sonos network traffic by making the packets too large for the network transport by tunneling them, there is a great post on it somewhere. A BOOST is highly recommend as it bypasses most of the router for Sonos traffic.

thanks both, I have just read about the problems with sky Q mesh/routers and Sonos. 

I was under the impression that if I connect my Sonos ONE via ethernet then it would act as a boost?  I could be mistaken.  This is why I changed from a wireless set up to connect at least 1 Sonos device via ethernet.

I missed that, yes, the wired ONE is a good substitute, but I wouldn’t put it on a Powerline adapter though, wire it directly to your router. Also check the WM: settings for your players to make sure they are all using SonosNet instead of WiFi.

It does seem that SKY Q mesh was the issue.  I disabled both 2.4 & 5ghz wifi bands on the main Sky Q box as we don’t need the mesh and reconnected all Sonos devices.  I think the problem was when my phone automatically jumped from the sky router wifi to the sky Q box mesh wifi it suddenly couldn't find the Sonos system.  Seems to be behaving now.

thanks both.