If it's the 1.4 HDi engine it's 144,000 miles or ten years.
If it's the 2.0 HDi engine it depends on what the service intervals are, it should tell that you in your service book.
If your service intervals are 12,000 miles the belt needs changing at 96,000.
If the service intervals are 20,000 miles, the cam belt needs doing at 90,000.
its not too bad if the belt goes on one of these, its not a head off job usually u get away with changing broken camshaft fingers. (and a new belt of course)!!!