Its a hard one to call. We've repaired loads of these engines from waterpump failure and the odd non-waterpump related cambelt failure and the mileages vary wildly, from 30-something thousand to failing 3 days before coming in for a 72k service.
But we also change lots of cambelts on JTD engined cars that have made it to 72k, and we always change the pumps. Sometimes they are just hanging in there, sometimes they are alright with very little play.
I'd draw my own 'comfort' line at 4years & 50k if I owned a JTD 16v or 20v. But because there is no official line on this and failures at lots of varying mileages are reported, it really is hard to justify one arbitrary change interval vs another.
I think this is the most balanced view, its 36k for the TS and JTS but the JTD engines are a lot more solid in respect to the cambelt side of things. also consider that a belt failure on a derv is less likely to result in the engine being beyond repair.
they use a lot less oil in general as well, although there are bound to be a few exceptions.
as with all of the GT cars regardless of engine suspension is a known weak area front especially, as well as electrics niggles.
I recently purchased a diesel and negotiated a cambelt change along with all related ancillaries on purchase.
I have no plans to go near it in that respect for at least 50k which for me is around 2 years on current mileage, EGR has been blanked and the car has been re-mapped so by my reckoning a swirl flap delete at the next cambelt change will ensure the lump will cover 200k plus with regular servicing.
if i were you i would be looking at belt and pump for peace of mind and a nice little map and EGR delete to improve economy ,drivability and minimise the likelhood of swirlflap failure.