Now tested some voltages - the input from the transformer seems OK but pressing the micro switch produces no change in resistance across the white and red wires.
Unless I can bypass the microswitch loom to test the motor directly (any suggestions?) I have to assume the micro has died.
Just moved into a house with an Aquastream 2 shower:
http://www.showerdoc.com/aqualisa-aquastream-thermostatic-manual-post-1997-shower-spares
It worked for 10 days then stopped other than allowing cold and hot through the pipework in a trickle, ie. no pump assistance.
There seems to be...