I have recently visited a customer who has exactly the same problem with her 10.5 SCL shower -- totally cold running but electrics appear OK.
The manual has a fault diagnosis table, which if I remember correctly states that one possibility is that the cutout has operated, and that -- wait for it! -- this is not a user-replaceable part and a 'new unit' must be purchased. (Or words to that effect.)
I interpret this as meaning a totally new 'innards' (replacement shower engine) costing about £50 depending where you buy it!!
I might buy and fit this for the customer, but having read this posting (and similar ones) I might recommend she lets me fit a different make (e.g. a Mira), which from my experience has never suffered from this permanent cutting out.
Alan Kauffman
November 2007