The PLAY:1s do not have a good enough processor to allow them to be AirPlay 2 targets. You would need to either group them with a Sonos One, which can be an AirPlAY 2 target, or set them up as surrounds with a Sonos sound bar, which would then get the audio through a connection between the sound bar and the TV, and send the surround information to the PLAY:1s via Wi-Fi.

Thanks for your reply, sorry I do have the Sonos ones but I put wrote play ones by mistake, thought that I would need a play bar as a link to the speakers, just to clarify though will the Sonos ones work by themselves without out the play bar when watching movies as Itunes speakers show up but when I select them the video switches off due to speaker selection being selected and Apple TV is un-selected 

Thanks again Steve 

Your run on sentence has me confused.

Are you watching something using iTunes on a computer, and “casting” that to your Apple TV using the AirPlay 2 network, and then also trying to use AirPlay 2 from the computer to send the audio to a second device, the Sonos Ones?

To my knowledge, that won’t work. I think you could use the Apple TV to connect via AirPlay 2 to the speakers, and then use the computer’s AirPlay 2 to connect to the Apple TV,  but it’s not possible to have two separate AirPlay 2 streams, one for video, the other for audio, from a single device. This is an Apple limitation, has nothing whatsoever to do with Sonos. 

If I’ve misunderstood what you’re attempting to do, please let me know. 

In short, yes the Ones work as target for Airplay 2 and don’t need a separate Playbar to work. 
 

But they are audio only, so if you try to Airplay a video directly to the Ones, you will only get sound. 
 

So @Airgetlam is right: you need to cast the video to you Apple TV and then set the Ones as speakers on the Apple TV: Push/slide down on the Apple Remote for the Apple TV and choose the Ones for audio.