Now done a short Blat, and the cycling seems to have stopped, so the switch must be faulty.
Will attempt to change it as soon as I can get a new one.
One other concern, according to the Stack manual, when I turn the ign on, a low oil pressure should display and the red warning light should come on - neither happen on mine, is this a Caterham feature?
Thanks again everyone for your earlier replies,
Bob