A: Yes this should stop the water entering the unit
See below this may be of some help.
The pilot valve is a common fault
Turn off water and power
Put something in the waste just encase you drop a screw!
Remove cover
Remove splash plate at pipe entry
Remove 4 screws from 'U' clamps and 'U' clamps
Later models have “Torx” screws so you will need a “Torx” screwdriver with a T10 Bit.
Remove screw above letter 'A' on drawing
Ease pilot valve forward (if there is no movement on the pipe work you will have to disconnect it at the inlet connection take care to hold the brass body with pliers when slackening the nut)
Swap the wires over from one pilot valve to the other one by one
Then reassemble
Turn on water and allow the water to come thru unit before switching on power.
Easy init!!!!!
Link to Pilot valve
http://www.showerdoc.com/shower-spares/mira/MIRA-419-87-Pilot-Valve Answered 792 days ago | The Doc