After 'boiling' the engine in molasses for two weeks, its now clean of scale and rust - just incredible what came out of it.
Pulled the engine studs out, after reading about this process, I took it easy but found that only two of the studs made a cracking sound, the rest were a fine line between "are they shearing or coming out".
Finally got the hang it after braking four studs (oops). Best process was heat the stud, cool, test, reheat and retest. Some really stubborn ones came out after about six sessions. I used this bearing type extractor as it grips very low and it worked awesomely.
Engine is now completely stripped and goes into the workshop tomorrow.