Have you perhaps disabled the wireless radio on your Beam and/or surrounds?
Have you tried powering ‘off’/‘on’ your Sonos devices and your router too?

If practicable, what happens if you cable your Beam to your router?

Are your WiFi network credentials stored in the controller App network settings and shown as being either ‘in use’, or ‘previously used’?

Thanks. 
I tried your suggestions and I was able to reconnect them for the evening. However this morning the issue has raised its head again and am back to square 1

Can you briefly describe your network setup. Make/Model of router and if you are using any other wireless access points, or hubs. Any network switches (managed/unmanaged) etc.

Did you try cabling your Beam to your router (if practicable) to run the devices on SonosNet rather than your routers WiFi signal?

The two Play:1 surrounds actually connect to your Beam ‘direct’ over an ad-hoc 5Ghz connection, so I’m also wondering if you have anything else nearby that might be interfering with that band. Troublesome items can be baby monitors, microwaves or some ornaments etc. 

Did you try powering off the Beam and surrounds for 30+ seconds?

I have been having a similar issue. My current surround sound setup constitutes of a Beam, 2 x Play 1s and a Sub (G3). The past few days the Play 1s are not connecting to the surround sound. I can set them up as individual speakers on the S2 app but it won’t connect to the surround system. Similar to Lewboy I get the (+Sub+?+?) in the System list.

However, I logged on to the website and there is a notification there that the Play 1 is NOT supported by S2. 

My Wi-Fi set up is:

Vodafone provider

Google Nest mesh set up

Sonos is set up over Google mesh (no Sonos speakers hard wired).

I have rebooted the speakers and the router multiple times to no avail.

Help. 

It’s often suggested in various threads here, that if using Google nest WiFi alongside Sonos, that things often work best by wiring a single Sonos primary device (so not a surround or sub) to the primary Nest hub to switch the Sonos system over to SonosNet and then see if it works best on either channel 1, 6 or 11.

It may seem somewhat irrelevant to the HT surrounds as those use a 5Ghz ad-hoc connection to the Beam, but my thoughts are that the Beam is struggling to get a connection to your LAN - so wiring a Sonos device to the primary hub might fix all for you, particularly if you can perhaps cable the Beam to the primary nest hub (if practicable). So perhaps try these things and see if it works for you.