Really thanks for all you research, I can relax tonight and enjoy my favourite tipple instead
Yep, clear as mud, but on balance I'll probably adopt your approach which seems the sensible way forward. Indecently I did syphon some coolant earlier which actually was remarkably clean and free of debris but again, yes, good idea to give a thorough flush. Off tangent but slightly related and I've forgotten him name for the moment but GS at Aylesford have a guy in their workshop that worked on our cars when they were contemporary.
Best wishes
Nick