Hi Dave .
The rule of thump for a timing belt is every 60.000 miles or 98.000 Km.
Some say more but i would try and stay with the 60.000 miles as this engine is an interference engine
meaning if the belt does break you are going to get piston to valve connection and bend the valve , push the valve up and snap off the rockers .expensive little mistake on being late with belt change .
I suggest at this time you also change the following .
Valve cover gasket .
Timing belt idle roller .
Timing belt tensioner .
Cam and crankshaft oil seals .
Replace coolant with new .
and glow plugs if never done .
Still need additional information then please get back to me with the reply button, and not the poor or bad service, this way i can get back to you or suggest another expert if needed.Your deposit does not pay me until the answer is rated in a positive way,A bad rating does not constitute a refund.If you are not happy or you have sorted out your problem before the answer then please let me know with the reply button .Kind regards Greg.