Hi
I had the same problem, so I contacted the nice people at ShowerDoc.co.uk. This is an excerpt from their email:
Unfortunately there no maintenance instructions for this valve.
However to get in to this valve to replace the on / off seals you need to undo the large knurled ring (Red Arrow) to remove the temp control you need to undo the smaller ring ( blue arrow)
Remember to turn off the water and isolate the unit from the power supply before starting.
Oh dear - the diagram won't copy. Never mind, the large gnarled ring is directly under the micro-switch, clearly visible on the mixer valve in the Installation Instructions. It should unscrew by hand. You will need to replace two seals on the hot and cold inlets. I was supplied with spares when the shower was installed in a little bag with some grease.
Peter
July 2010