Steerpike,
Just a heads up that there are Watercops available with extreme discounts, , I have one of those and I learned later that it has an outdated firmware and results in disconnects from the zwave network. The work around I have employed is nightly power cycle via a scheduled smartplug. Which to date, knock on wood, the watercop rejoins the zwave network after the power cycling. Not ideal. Otherwise the watercop seems pretty beefy.
Watercop I believe is a rebranded Fortrezz.
Otherwise, deployment of leak sensors is a guess, as you can imagine the leak could occur anywhere in your home, hopefully your leak sensors are in the right spot…