Today, I removed the glow plugs and raw water poured out of them, blew them out, replaced plugs and restarted. RCR arrived and determined that the was a small airleak in the exhaust/cooling system that allowed the raw water to slowly siphon back through and enter the exhaust ports at the pistons. He tightened all jubilees (which all had slack in them) told me to close the aforementioned stopcock to stop any further raw water to be siphoned back (I now know I should be closing this every night as good practice anyway!) and I need to replace the o ring on the lid to the box with the raw water cage filter in.
Hope all that makes sense to you tech guys and thanks again for the quick and detailed feedback, every day is a school day!!! B