How can I clean a saniflo pressure switch?

I have removed my saniflo and taken the top off it because it was taking a very long time to pump the bowl clear in bursts of operation separated by minutes. i had been advised by an experienced person that the pressure switch may well be affected by scale (live in London very hard water) and have been advised to clear it- but where exactly is the pressure switch? is it at the base of the electrical section? Having got this far i'd appreciate any help!