Thanks to the contributors, you might have just saved me a load of cash and awful language.
I didn't need a spanner or a drink afterward, thank the gods.
I had the 'stuck on' issue. You need a strong magnet (I suspect strong).
I read elsewhere that the pump will shut off if it over heats (after approx 10mins). I didn't want that feature interfering with my diagnostics, so I turn the leccy/power off frequently while fussing with this stuff.
I have a mild water hammer effect that I don't want to fix as it is a diagnostic tool for leaks and kids leaving taps running.
When the pump stayed on, I was confident that I didn't have a leak or running taps.
I confirmed this by powering off the pump and closing the out going valves (I have a twin pump) on the flexi connectors
and turned on the power. The pumps sprang to action, so this isn't a leak.
IMPORTANT. Open the valves on flexi connectors again.
Tried the magnet (mild and strong) on the reeds. The pump didn't stop.
I turned off the power and released the zip tie on one of the reeds (cold). I turned on the power and the pump fired up, I tested the magnet against the released reed, both ends. Nothing, pump still running. Powered off and re-attached.
I released the other reed (hot), power on, nothing, no pumping! Bingo, double checked, by using the magnet on the reed, both ends and the pump fired on and off.
This means the reed and the control board are good. So it was the magnetic float in the hot outlet that was stuck. I took the strong magnet and stroked in a downward motion where the reed is to be attached a couple of times, then tested with the reed. The pump fired on, so I removed the reed, and used the other pole of the magnet. Opposing poles forced the magnetic float to free itself. I held the reed back in place the pump didn't fire, perfect. I cycled the power, all good the pump didn't come on.
IMPORTANT. Did you open the flexi connector valves from earlier?
I then tested at the taps that are fed from the pump. Everything worked the pump shut off when the taps did.
I firmly reconnected the zip ties on both reeds and verified all valves were fully opened.
I accept that if the float jammed once, it will no doubt do it again. But I have a low effort, low impact do-fer fix now.
Thanks to those here for the ideas and pointers.