Reich Karma microswitch

Hi, first a disclaimer, I don't have a caravan but do have a motorhome but think my query is common to both and hopefully very simple.

Bathroom tap is Reich Karma with pull out shower hose. Problem is no water from tap unless I turn kitchen tap on first so pretty sure problem is the micro switch. 

I have 'shorted ' wires so bypassed the microswitch ant and once 12v switched on pump works and the water flows but not ideal.

I've removed the cap of the top and can see that the microswitch is fixed in the cap  but not sure how it's held in place and don't want to force anything and cause more damage.

Does anyone know how the microswitch is held in place and how it is removed?

Thanks