Had to widen the diameter of the pipe outlets to aide water flow as this is where the inexplicable leak was coming from. Water was just backing up in the pipes as drains couldn’t keep up with the pump, and turning the flow of the pump rate down meant there wasn’t enough water going around the system. Ergo: wider pipe outlets. I imagine users will be discouraged from trying out the system if they’re told they have to fiddle with working out flow rates. All works swimmingly and no leaks now.
Also some plants aren’t faring too well. Maybe just because I’ve had the pump turned off for a little more than a week until I got the time to fix it. Suspect it may be nutrients or the cold though! Parsley is loving it.