The handbook for my '04 roundnose JTD 115 gives 72k miles / 5 years as the change interval for the cambelt. You should also get the water pump changed at the same time as a seized pump is often the cause of cambelt failure. As the aux belt has to be removed to get at the cambelt, it's although worth inspecting that to see if it's due a change, along with its tensioner.
The cambelt is at the opposite end of the engine to the clutch and gearbox, so there's not much to be gained by doing cambelt and clutch at the same time, other than the car will only need to be off the road once rather than twice!
FWIW, the service schedule for the JTD 115 is given as:
Cambelt visual check every 36k miles (replace as stated above)
Exhaust gas emissions - check every 24k miles (though this will be done at MOT time anyway)
Fuel filter - every 12k miles
Air filter - every 12k miles
Check transmission oil level every 36k miles
Engine oil & filter - every 12k miles (though I wouldn't leave it that long)
Pollen filter - every 12k miles
Drain condensate from fuel filter housing - every 4,500 miles or 6 months.
That's aside from the usual check and lubrication as required of door hinges, handbrake mech etc etc.