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Good day, I largely agree with Oldgoat. Lister made a lot of generators based around their S series engines (ST, SR, SL). These had two solenoids mounted at the governor end of the engine. The front one is the fuel control solenoid and is connected to the fuel injector pumps, when energized it releases the fuel control racks allowing diesel to be pumped up to the fuel injectors. This solenoid is a latching solenoid with two coils and a small internal relay switch. During the start up process, 12 volt dc is fed through the two coils opening the fuel supply, once the solenoid is open the small relay switch is triggered turning off the voltage to one of the coils and the solenoid is able to stay open on just one coil.
The second solenoid is a 240v unit (110volt for US models), this is connected via a spring loaded linkage, to the two decompressor levers on the top of the engine. During start up the engine spins up without compression, as the generator head starts to produce electricity this flows to the solenoid coil opening it and pulling the two decompressor levers into the run position allowing the injected diesel to ignite.
These engine would have been set in the factory for 1500 RPM for a 50HZ generator or 1800 RPM for a 60 HZ output. My ST2 had some throttle adjustment available to fine tune the output.
Hope this is helpful,

Bob

Just editing this post as answered own question - so I appear to have a Start o Matic missing the control panel which the previous owner seems to have been running on a manual start.

Hello all

I managed to pick up a CS last weekend (in Scotland), serial no 35 81  513 - so I guess an 8/1, any other info on date would be much appreciated.

Half way through stripping it, looks like it should run.

Thanks!