Upload all your music to iBroadcast.  It is a free, cloud based storage for your music library.  iBroadcast can then be added as a streaming service in your Sonos app.  Works great.

You can use the Music Library facility if your iTunes music is on a NAS or hard drive somewhere?

Some years ago there was something like “on my phone” but Apple changed something and stopped it. That was prob what you were using. 

Thanks – ah it is actually a Play:1… but I’m sure I used to play my iTunes through it? 

I did try to add iTunes but I don’t have an Apple Music account so I couldn’t do that.

So as its a Play:1 is there no way to play the library of music thats stored on my phone – only streaming services?

It’s a One, not a Play:1 that you own? Play:1 is older and doesn’t support Airplay. 
 

Have you enabled iTunes/Apple Music in the Add Music Services part of Settings (cog icon at bottom right of phone app).