Graham,
Remember that if your iPad has ever connected to someone else’s PAW (in my case, for example, when checking something on their device or helping them setup or update their unit), that is then a ‘Known Device’, which my pad will potentially reconnect to again in future (unless I physically ‘select’ that device’s WiFi and tell iOs to ‘Forget This Network’. For this reason, I have got into the habit of always checking my WiFi connection prior before takeoff after moving away from the Clubhouse / Apron .
This is of course easier if you change the SSID in the Network Screen to something easy to notice, like your Aircraft Reg. I presume you are aware, but for the benefit of others reading this, if you do decide to set a password, take care to make it something you won’t forget, as the only way to get back in if you forget the password is via a complete software reinstall, or by establishing a hardwired connection via a router / LAN.
Regards
Peter