how do i remove my sonos from spotify connect

You should be able to break the cloud link just by playing another source on it

 If you change your wifi password that will prevent him from repeating the trick if you ever let him in your home again.

I must admit I am amazed the steps you have already taken have not broken the link.

"Remove a speaker from Spotify Connect" doesn't really mean anything 

Unfortunately not John, this is spotify connect, once you have connected to a device it is then listed in your Spotify app see the picture below

 for example even if I am on 4g and WiFi off off on my phone I can still control it 

As John says, if you play a non-Spotify stream on the Sonos, that will ‘break’ any Spotify Connect sessions from anyone not on your local network. 

I have played local media from my phone but he still seems to have control when he wants to sadly 

Are there any other SONOS units in your system? If so, using a SONOS controller, make sure that no Rooms are playing Spotify. If you see “Started from Spotify”, play some different music in that room. This will break that remote Spotify connection.

Yes, that’s my understanding too - once the friend is no longer connected to the local WiFi network and a different source is played to the speaker, like playing music from Sonos Radio for example - that the friends Spotify account will not (cannot) reconnect to the speaker, unless you allow them back onto the local WiFi network.

They would otherwise need your Spotify account login credentials. 

Surely if this was possible (not being able to break the link) Spotify Connect would have disappeared in a storm of protest. It would be chaos, anarchy.

Other than getting on his phone and pressing this forget this device I don't know what to do. 

I have tried another source on my phone through the sonos app and then switched off WiFi and it was still listed as a device I could control in Spotify.  I only have a sonos one no other devices

How are you testing this? Playing another type of stream on your Sonos, when your friend is no longer on your WiFi, breaks their connection via Spotify Connect to your Sonos. It would have zero affect on your own device, as you are the system owner, and on your own WiFi. Unless you’re calling your friend and asking them to test, you will see/hear no change. 

Other than getting on his phone and pressing this forget this device I don't know what to do. 

 

I have tried another source on my phone through the sonos app and then switched off WiFi and it was still listed as a device I could control in Spotify.  I only have a sonos one no other devices

I think a local source should work to break the link, but try Internet radio.

You say it is listed as a device you.can play to. Did you.actually play through it?