Thanks to everyone who took time out to reply to this post.
Having checked everything relevant to the fault I decided to follow up on the advice posted by tony about the issue with the hydraulic tappets. Although the vehicle is registered a 2008 it is the earlier RFN engine and fitted the symptoms exactly.
Using an engine flush (BG quick clean) I replaced the oil and filter and there was a marked improvement in the cold start up and no anti pollution light!
So far so good a week later. So now to find out the cost to replace will post if we go ahead with the replacement.