Bosch Clasixx 1200 Express Overfilling

Hello.
I have a WFO2467GB/01 FD8507 606302 that is about 2 years old and which has been used about 4 times a week. It has recently started overfilling and not spinning. On a normal wash cycle, the water is drawn in but rises to a level higher than normal – about 2/3 up the door glass. It then can be heard flowing out of the drain hose, the level drops a bit but then more water is drawn in to replace it. When drain is selected, about half the water is drained out then it stops. If drain is selected again (and possibly a third time) the machine is then empty. When spin is selected, it drains, but never activates the spin (with or without washing inside); the number indicated goes straight from either 12 or 11 to 1.

I’ve checked and double-checked the following :-
Outlet hose positioning / drain / length in drain / height etc. (though this hasn’t changed at all over the 2 years)
All hoses out of the bottom of the drum + connections
The sump ball
Pump – have seen the impeller happily spinning when activated through the drain hole at the front (no water in of course)
The water level system – the cylinder at the bottom had only a tiny bit of gunk in it, definitely no holes in the pipe to the pressure switch
Pressure switch activates when you take it + cylinder + pipe out and try lowering into a bucket of water or blowing down the end

After reading the posts on this forum, a faulty pressure switch could have been the problem so I obtained one through yourselves (thanks). The first test I did was successful – spin cycle (no washing) seemed to drain what little water there was and start spinning. So I filled it up with clothes and started a regular wash. It overfilled again and the same symptoms as above are still occurring. 🙁

So I’m now thinking that the pressure system is probably working ok, yet the signal is not getting back to the controller for some reason. So is there a simple test to prove that the pressure switch is activating please? Noting that the connector is effectively sealed / moulded and I have experience of electrical testing + equipment. Or, is there a way of simulating the action of the pressure switch somehow?

Any help gratefully received