I have followed these steps but there is no option to Update network.

1. Open the Sonos app and wait while it searches for your Sonos system.
2. When the Sonos app shows “No products found,” select Go to System Settings.
3. Under Your System, select Update network.

There’s almost never a good time to factory reset a Sonos system, unless instructed to do so by Sonos Support . What I’d recommend on your case is to temporarily wire an Ethernet cable to one of your speakers. Wait 5 minutes for them all to recognize the change, and show up in your controller, then change the network information in your controller.

Do you use S1 or S2 in your system? What is a Dreamcatcher? 

Did you read the new router - installation instructions FAQ?

Thanks Bruce, but not possible to wire an ethernet cable. I don’t know what S1 or S2 is. A dreamcatcher is some kind of system that ensures your internet never drops out! 

I’ve started the factory reset, so god know how long that will take!

For other users discovering this conversation— the factory reset results in a LOT OF EXTRA WORK. The easiest method is to install the old WiFi name into the new router, then reboot all of the network clients.

Minutes if you are lucky, days on the phone to Sonos support if you aren’t.

Sonos are easily portable, far easier to carry one close to your router and wire it in than the often iffy factory reset that leaves you with a naked new system.

Just to let everyone know, the factory reset took about an hour, but the system is now working fine. Thanks for everyone’s comments. Technology is not my strength so I appreciate everyone’s advice.