Yes there is. You will first have to set them up as an S1 system on your wifi network. Then set up Autoplay on the lines in (you might as well do both). Then you can use them standalone with a source in the line-in (including a Bluetooth adapter if that is your choice).
Note that you don’t need Internet to play local sources, you need a LAN. So a router without a connection to the internet would provide this, and allow you to (for example) play music stored on an Android phone without the need for Bluetooth.
Many thanks for your reply John B, one more question, does the LAN have to be the same one that I set up the S1 with ?
Many thanks
Doesn't have to be the same LAN but if you use the same network name and password it may simplify things.
Given that you can put the router anywhere, I would put it by one of the speakers and connect by Ethernet. The other speaker can then connect over SonosNet.
Then connect your phone to the WiFi for control.