Hi Adrian. Myriad possibilities and probably many you will have tried - but if it helps anyone? No knowledge of Water wiz 2, but looking at all my timers there would appear to common points. Let's start at the beginning. Disconnect any hoses and fittings attached to WWz. Turn off tap to unit and ensure unit is not set to supply water. Turn on tap. Is any water apparent. I have had a few issues with fitting to tap leaking, water dribbling down back and appearing at the bottom as a leak. If leaking from tap fitting, 'Nip' up tighness and check again. Check washer in connector and replace. Fixed?? OK no leak from connection. Is water still appearing at bottom - consider a hair-line fracture from either over -tightening connectors OR was unit exposed to frost. Get a new one and remove before your expected first frosts! No leaks, then check hose connectors on outlets. The rubber washers harden over time and either need a further 'nip' up from finger tightening, or replace the washers. Ensure hose is properly connected to hose connector and hose connector firmly 'snaps on ' to unit nipple connector.
Hope this has helped. Cheers.