Sounds like your router is challenged. Can you add a proper router? If not, just disable 5GHz on the one you have and see if that improves things.

Usually you can put the ISP supplied router in Bridge Mode and connect a proper router, aside from getting your Sonos working a better router usually offers better services and options.

Thank you, I will try disabling 5ghz, but what do you both mean by ‘proper’ router? It’s direct from Vodafone, and supposedly their latest?

Another user recently reported the same issue with using the Vodaphone router.

Whilst the ISP’s router may be their latest, that doesn’t mean that it compares favourably to purchasing your own router, which allows full customisation of your network, which isn’t necessarily possible with an ISP router.

ISP routers are generally bare-bones with primitive or half-implemented features. They are cost-reduced to basically be a NAT gateway for web browsers and can be a challenging when actually used for more advanced features, in this case inter-device data transfer over the local network.

Thank you for the replies, I wasn’t aware of these problems as there’s not been any problems when I’ve switched over routers before. 
I’ve got home this evening to find that more of my speakers have disappeared including individual ones that are paired with another that working.

So I’ve delved deeper into the router settings, I now have 3 nets, a 2.4, 5 and a third 2.4, 5 and 6 GHz combo. I plan to connect Sonos to the 2.4GHz one when I get some time. I’m assuming that I will have to reset every single speaker again and this will save me from having to hard wire my beam in? 
OR would it be better to hard wire one to the router and set up a completely different net?

If you do attempt to change the Wi-Fi credentials, certain players without Bluetooth Low Energy (BLE) need to be reset in order to receive new network information. See Unsupported Products here https://support.sonos.com/en-us/article/connect-sonos-to-a-new-router-or-wi-fi-network

Connecting using wifi is the Sonos recommend, method for most users.

Using a wired connection, moves you to Sonosnet, that is older and no longer fully supported territory. I redid my setup to remove multiple Ethernet connections and use onls wifi and things are more stable,.

No longer fully supported in the sense newer devices and portables are not compatible with SonosNet, but a wired system is still fully supported from a support point of view.

​@NicB74 

I’m late the party….again….but here are my thoughts

I’ve read your post and it appears that your ISP upgraded your router to WiFi 6 also known as 801.11ax.

Those routers will work with Sonos as long as you use the same SSID for all bands and disable band steering.

I have a (personal) WiFi 7 router (802.11be) and my Sonos works fine. However, as others have said using your own router is best for flexibility and feature access.  

You should also use the same SSID and Password as was previously on the router that was replaced.

Here’s the most critical part of changing router (personal or ISP provided) and should be followed in the order presented:

1. Do not reset any Sonos products
2. Unplug all Sonos
3. Setup new router as described above
4. Connect your device and check for updates
5. Delete the Sonos app 
6. Plug in your Sonos 1 x 1 and let them come back
7. Wait 10 minutes after plugging in the last Sonos (if you can see white LED on all units before 10 minutes then proceed to next step
8. Re-install Sonos app
9. Open the app and select “Join existing system”
10. Agree to ALL prompts
11. At the app Home Screen click the cog wheel in upper right corner 
12. Sign in with your Sonos credentials

That is not true.

I have a WiFi 6 router and use separate SSIDs for 2.4GHz and 5GHz without experiencing any issue with Sonos.

Well…that may be true in your case; but not in my setup. I’ve found that using the same SSID and allowing devices to select their band works better. Sonos specifically will ignore the incompatible bands. 

You should edit your post, qualify your statement. Because as pointed out it isn’t true. 

I have no time for this. I know what works best in my setup.

In the time it took you to post this response you could have fixed the misinformation. It matters because people searching for solutions may read it. 

Best practice is always to use single SSID and let the client decide what is best band to use, turn band steering OFF.

Of course you can split the bands with different SSIDs, but this is not best practice/recommended.

Is this Sonos saying it’s always best practice, your opinion, or?

Not sure why people are recommending one SSID when the OP stated in their initial post that not having split bands was the given reason for their connectivity issues.

Neither, its industry best practice. ISPs ship their wireless routers with single SSID for all bands, and band steering disabled.

I suspect its probably specific to the WiFi7 implementation on the ISP supplied router, is a Vodafone Ultra Hub by chance?

Thank you for all the advice, I definitely need time to go through all of the posts, then find the time to try to sort the system out. I appreciate everyone’s time and advice, I will get back to you with the results. 

Tried what AjTrek1 suggested. Now missing peripherals from both Bar and Beam, a play one and app tries to group other speakers but can’t. Also got strange icon and. The right of each speaker. 

That ‘strange icon’ represents how many ‘rooms’ are grouped. In the screenshot, you just have one room associated with each ‘group’ of speakers. If you were to group two of those Sonos rooms together, you’d see that icon change to a higher number. See this thread, which is pinned and highlighted at the top of the forum.

I thought that originally but none of them were grouped, and wouldn’t group!