This rather nice picture has come to light....
This pretty much confirms the point machine is a Westinghouse Style C.
My next problem is.. There doesn't seem to be enough wires terminating on the pole for control and detection. The two bottom wires on pothead insulators carry on through to the far end of the bridge. I have a suspicion they are 'power' wires but the power comes from a hand generator. All the signals at the far end of the bridge were motor operated. The Westinghouse catalogue lists signal motors operated by hand generator and held off by by a local battery. I have evidence these signal motors were of the Westinghouse type. I think i need to talk to an ex St I'ves signalman <g> I know more about Melton Constable than i do St Ives and theres over ten years between their closures.