Hi. You cannot store your Sonos Music Library on a phone or tablet. The way to play from an iPad is to use Airplay, but unfortunately the Play:5  gen 1 is a rather old speaker and is not Airplay compatible. 

The cheapest solution would be to get a Bluetooth receiver and connect it to the line-in on your P:5.

The music is on the same iPad as the Sonus app so are you saying it cannot find it from there.

thanks for you help.

Yes, that’s what he’s saying. Sonos doesn’t allow the Sonos library to be on any mobile device, be it an iPad or an iPhone, or the Android equivalents, as they can easily leave the network at any time, leaving any other users bereft of music.

Sonos does allow you to play from music stored on PC/Mac, or even an NAS. Or, if you have an Apple Music subscription, from the Apple Music servers. 

Apple closed the loophole many years ago that several companies were using to allow playback “from this device”, so at this point, if you’re playing music stored on an mobile device, you must use, as @John B suggests, AirPlay 2 (for those speakers that have it) or Bluetooth, by placing a Bluetooth receiver in the line in on your PLAY:5 gen 1. 

Many thanks for the clarification, how would I connect my play 5 to my desktop to access my iTunes music, would I require the Sonos 1 app on my desktop for staters and would I have to connect via Ethernet cable to achieve this?
Please do not underestimate the much appreciated help this community can give to an old git with limited tech ability.

See this article for setup, which is easiest done using the desktop controller.

https://support.sonos.com/en-gb/article/add-your-music-library-to-sonos

Once it is set up you can play from it using any controller.