You can leave the Playbase under the sane system, if you prefer, and just add your Summer House WiFi network to your current system in ‘Settings/System/Network/Manage Networks’ and use the ‘Update Networks’ feature in the mobile Sonos App. (See example screenshot attached).

Or you can just reset the Sonos App and setup a new system at the Summer House - then add the previously reset App back to your "existing" Home System - this link explains how to do that:

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

Thank you Ken. I will try next time I am in my house !

Best regards,

Xavier

Update

Solution #1 did not work: while in my summer house, I cannot access the system menu (because the existing system cannot be found ?).

Solution #2: I tried to follow the instructions from the App (system cannot be found), but it only gives me the option of finding my existing system, not a new device ... Thus the need of reseting the App (as you suggested). Before proceeding, do you have instructions for adding the previously reset App back to the existing home system ?

Thanks for your help