Ok this has me worried now...
1st check - the knocking does not seem to increase it goes away between 600 and 1000rpm
2nd check fluid levels - gearbox level fluid still red and on the O in hot so thats ok
I have discovered its coming from the back of the engine perhaps the gearbox perhaps not, either from the top of the gearbox or the cylinder head the car idle's at 530rpm and when you click it into drive or any gear it dips to about 490-500rpm which is probably to low.
The knocking sound is very prounced when it idle's in gear then when you rev it the sound goes away, take it out of gear the sound is still there but fades away and is alot quieter.. increase the revs (not by much say to 1000rpm) and it goes away.
I thought i would check the engine oil and its still between the markers (on the higher side of the marker) and have had it replaced not long ago so nice and golden still.
I have noticed the sound is only there when the car is warm and down to hot idle, the car still has power and again the sound goes away when driving (sounds loevley and smooth) i am stumped now, if its a bad big end shell then surley it would get louder and deeper when more power is applied.
Help !