Thanks, that does sound like a feasible explanation and I am leaning towards the DMF as the issue it was just that the mechanic who examined it was sure that it was ok. The three pressure fingers that are worn are the three in the top left hand quarter of the first photo. The noise it is producing has gone from being loud and almost constant to a quiet, intermitant 'snick' type sound. There is clearly still some contact and I suspect that the next step will be to replace the DMF unless anyone has an alternative suggestion.
Thanks again,
Steve