Well, I have done it.
I am now the proud owner of a complete CS 6/1 SOM. (IE it includes the separate controll box that is so often missing!)
I bought it off E-bay (UK). some might think that I paid a bit over the odds but the difference between a "Fair" price and what I paid was only a couple of hundred quid at the most and in the great scheme of things I reckoned that it was more important to have a complete system. the real expense will come later as I restore it to reliable operation.
I only had a small trailer to recover it and I actually think I was Lucky that it didn't collapse under the weight getting it home (No seriously!

I had considered that the 6/1 was 330KG and the cast iron base not more than 150 KG. Now I read that the SOM engines are actually nearer 500KG owing to somewhat heavier flywheels. The weight of the base I do not know! The generator was removed and put in the back of the landcruiser to reduce the load on the trailer but it still must have been somewhat more than the 500KG rated load capacity!)
Thus far I have not even got it off the trailer (This will be fun) It turns over smoothly but I am clearly not getting compression (My guess is that the exhaust valve is not seating owing to it spending the last 5 years open on the decompressor)
I have no real issues with getting the engine to work but I am more concerned about the SOM alternator and controll boxes. The controll boxes both require complete restoration/rewiring and the cables between the alternator and the top controll box are in poor condition (Insulation brittle and cracked)
I would be gratefull if anybody who has had experience of repairing the controll boxes and alternator would be willing to share their experiences.
Photos to follow!