My van is fitted with a Thetford C200 the electric version The problem I had been having is with the electric switch despite sealing the best I could, they just rust out, even with the tank empty it seems you only need a dribble of water in the fresh water tank, and the condensation will rust the switch.
Well after 3 replacement switches at £25 a time, I decided to convert the toilet to a manual pump the whole thing was £25 same price as the switch. All went well until I had the dreaded pink flush fluid growing black algae, blocking the flush and putting pressure on the pump, breaking it.
So I'm back to square one. I decided to reinstate the electric pump while away in the van by first unblocking the flush blockage with diluted bleach and some wire. I had an old 12v switch that was used on a car and that got us by for the holiday.
On my return home I set about finding a switch on ebay, the horn push type, and low and behold I found the very thing for just £2.89 inc P&P. All I needed to do was drill out the place where the Thetford switch was to 26mm, and drop the new switch in, and it work a treat! I have ordered up a spare in case it rusts away but to be honest it's much better quality than the genuine Thetford replacement.
So before you order a £25 original check this option out.