Using SONOS with BT Smart Hub, UNIFI HUB and MESH

Assuming your UniFi WiFi has reliable coverage where the speakers are (you say you have 4 APs, so must be a big home), I would reconfigure your Sonos to use the UniFi WiFi, and then remove Boost and any other wired speakers:

https://support.sonos.com/en-gb/article/switch-sonos-between-a-wireless-and-wired-setup

Ensure you have disable the WiFi on your BT Hub and only use the UniFi APs for WiFi.

So you’re saying turn off WiFi on BT HUB. Just connect it to UNIFI UDM for provision of internet essentially using ETH. Then use the UNIFI network as only WIFI one.

Remove the Boost and ensure all speakers connect via WIFI only? So no speakers hard wired via ETH. I think coverage should be sufficient.
 

Would you suggest changing the network name and passwords on all UNIFI devices to something new? Then rebooting all SONOS devices and re-adding to the new network? Or just leave the SSID and Password as is? 

Thanks for the swift reply. 
 

Yes, turn off the WiFi on your BT router.

Reconfigure Sonos to use WiFi, disconnect ethernet from all Sonos devices, power off boost, as per the link I sent above.

No need to change SSID or password on UniFi, leave as is, you don’t want to reconfigure all your existing WiFi devices.

Is it BT FTTC service, ie phone line, or FTTP terminated as Ethernet?

Thanks. Will give this a go Friday. It’s phone line and not fibre.

Your configuration is not ideal with a BT firewall/router plugged into a second firewall/router that are both NATing their WAN ports. Ideally you would want a DSL modem connected to the WAN port of your UDM, it may be possible to configure the BT router as a modem / bridge mode. You will need to check on BT / UniFi forums.

That said, Sonos should work with the double NATing, but is not recommended.