Factory Reset has complicated your issue. 

Likely the network you are using restricts users to Internet access only. If this is the case, while you can setup the ONE, the phone/pad cannot operate the ONE because the controller App must be able to establish a connection to ONE over the local network. The solution is to add a “Travel Router”. The Travel Router will establish a local network for SONOS and your phone/pad and allow them to access the Internet.

 If you can give us more detail about the network, there may be other approaches.

As I said, Factory Reset has complicated the project. Regardless of success using the unit while on holiday, when you return home I recommend that you Factory Reset the unit again — before attempting to use the unit, then add it to your system as a new unit. Be careful at this point. Do not set up a new system.

Thank you very much for this, I will get a travel router and let you know how I get on. I will be able to use it on other holidays 

If you cleverly use the same WiFi credentials on the Travel Router as you use at home, simply plugging in at the holiday venue will get your SONOS system going. If the venue is only wireless, you’ll need to enter the venue WiFi credentials on the venue side of the router.

I have just set up a GL.iNet GL-SFT1200  travel router and that is working for my mobile phone. However I still have the same issue with the Sonos speaker failing to set up. I get to the last stage of having put in the new network wifi password and it says problem setting up after a couple of minutes