I thought I would share my recent experience of getting my saniflo unit repaired - as I struggled a fair bit to find the right person. Basically, not all plumbers can repair these things and so the best place to find a qualified saniflo repair engineer is the following website:
http://repairs.saniflo.co.uk/
I called the engineer listed in my location and they were very good and no more expensive than a regular plumber. The guy found the issue straightaway, had the right parts with him and an hour later by shower room was back in use.
I wish I had known this before and save me a lot of time and effort