Thanks Clifford,
The engine does seem to run quite hot, the temperature gauge is normal, the oil does seem to have brown emulsion, yes there is a knock from the engine under load, but only at a certain RPM, no smoke from the exhaust. When the engine is cold & in neutral, if you give a short hard rev (say up to 3000rpm) there is a knock from the engine (but reduces when the clutch is pressed down), when ticking over its silent & the knock is less noticeable when the engine is warm.
Looking forward for any idea's you have,