Well, finally got my car back avec new engine... have to say the difference is DRAMATIC... no longer sounds like a tractor! Still the faint tappity sound (which I have been advised is from the injectors) but this dissapears with the slightest touch of the accelerator... as opposed to juts getting a bit noisier! Very happy with the car now.
Didn't get any specific running in advice, can I assume keep it under 40 on the rev counter for the first 500 or so miles? On the drive back from the garage I kept it under 3500 revs just to be on the safe side...
Dealer also fitted 3 brand new alloys to my car due to the dreaded corrosion... the other one was too badly kerbed to be done under warranty....
I will post a sound file with the "before" sound and "after" sound for anyone interested