The physical switch can be used to enable / disable the charge point or override a charging timer. If you want to secure the unit I would recommend an option for the option without the switch then the unit can be enabled or disabled via the local WiFi network. Assuming you will be giving guests access to the holiday cottage WiFi, once connected to the holiday cottage WiFi then will be able to connect the charge point and enable it. Or you could set up a remote connection to do it for them.
I do think it’s unlikely that anyone not staying in the cottage would attempt to use it, someone would need to plug in for 1hr to steal about £1 max of electricity, the risk vs reward is not good! Fitting a gate or CCTV would probably be more effective. I would recommend keeping the charging experience simple for guests allowing them to just plug and play to charge.
We decided to develop the EmonEVSE with a non-tethered cable as our pre-built OLEV certified unit since this is the most flexible option. If you want a tethered unit you can just leave the cable plugged in. I would recommend a non-tethered option for a holiday cottage since this will allow guests to charge EV’s with different charging connectors e.g older Nissan Leafs, mitsubishi PHEV