Nothing wrong with microswitch at all - but I'm a native English speaker and a non-native Swedish speaker. There are times I resort to Google translate for certain terms in Swedish (in Swedish which I'm guessing is similar to German, it would be a "fackterm") which are related to a specific areas.
That was what I was worried about... and now I see that it's all "kinematics box" which really messes with my language abilities
I've found somewhere that will supply those parts in the UK so hopefully I can try and get them installed and see if it will make any difference.
Thank you massively for your help. It has been really, really helpful.
I'm at my wits end with this thing, and like you said, it really doesn't look like a pump problem.