[puppy]

To answer my own question, the problem turned out to be that the driver's side door didn't have the right lock barrel. Maybe the door had been replaced at some time. Anyway, after buying a second hand lock with barrel and taking the door apart (no easy job) I was able to change and modify the wafers in the barrel to suit my key. This would have to be one of the most difficult jobs I have ever attempted. Changing a clutch had nothing on this. All good now. Cost me very little but gave me a lot of heart burn. Getting the inards out of and into a Ford Fiesta door certainly isn't any picnic. Try it some time. You'll save yourself an fortune and get grey hair. I'm already grey!