Either setup the Sonos One at the first location and add the ‘other’ WiFi network to the device when at the second location. (Or just use the same SSID/Network credentials at the 2nd location so as to ‘mirror’ the 1st location). Anyhow here’s a link on how to add a new router/WiFi Network to your existing setup…

https://support.sonos.com/en-us/article/connect-sonos-to-a-new-router-or-wi-fi-network
 

An alternative to the above, is to setup a new Sonos system at the second location by resetting the Sonos App on your mobile controller device and begin the system setup with the Sonos One in a factory reset state. Personally speaking, I do not prefer this option, but it’s entirely a matter for you. 

On return to the first location, simply open the previously reset App on the local WiFi network and let it find your existing Sonos system and choose to connect to it.

On connecting the Mobile device to the WiFi network at each location, when opening the Sonos App, it will then connect automatically to each system at that location.

Hi Ken, thanks for your reply, option 1 was correct but I also discovered I had been entering the wrong password which explains why I was going round in circles a bit. Cheers