CONCLUSIONS:-
1. Although it was a more expensive route (and not totally required) I am happy that I replaced the heads - they had the micro cracks between the valves - however, this eliminated any area of future concern and brought the compression levels up.
2. Replacing the hydraulic cam followers was a worthwhile move, this has certainly removed any valve 'knocking' that was present before.
3. Replacing the one corroded head stud was also an intelligent move - if not a scary one.
4. Despite most information I had gleaned from alternate sources the main cause (in this case) of the coolant leak was the bottom cylinder 'o' ring. It was a lower % possibility than the top cyclinder 'o' rings, or bad sealing around the head nuts, but in this case the cause of the problem.
5. All the work is possible without removal of the engine.............but it would have been a damn site easier if I had had the opportunity and the tools to have done so. The bruises on my ribcage and upper arms can testify to this.
6. The home-made tool for extracting the gudgeon pins works a treat.
7. A big THANK YOU to MAXSTU for his guidance and cheering from the sidelines certainly brought me back from the edge - cheers.
Oh and one final thing - don't try and put an exhaust gasket in the join between the water pump and the metal outlet pipe - there is a rubber 'o' ring there already (yes, dumbass here actually did that and wondered why it was dripping coolant from the join)
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And also for writing up with photos for others' to benefit from your hard work.