When does my cambelt need changing?

I have a ford fiesta 1.8 tddi on a 2002 reg with 55000 miles when do I need to get my cambelt changed?

Check to see if there's a recall on your vehicle, cam belts should really not stretch at 55k miles normally, they should live a bit more than twice that without problems. Simply the belt either stretched or jumped timing that damaged the belt.

The recommendation is 100k miles but that seems too long for me. Also if it's not been done, 12 years is far too long to leave it, there's a time element to them as well as a mileage one. If you value the car change it now, if it snaps it totally destroys the engine.

Most require it around 90,000 to 100,000.

If it's twelve years old then the mileage is irrelevant. Change it as a matter of urgency and avoid hard acceleration and high speed runs until the work gets done.