Hi Martyn.
My son's partner ahs got a TD4 manual(03) and they have a lot of bother with it.
Waterlaeks are frequent. It is ussed to tow a twin horse box and while it tows, it does feel under strain. They have also had a lot of wheel bearing replacements and brake pads don't last long.
Their previous TD4 (y plate) gave up it's gearbox via several shreaded gears. The cost of repair was higher than replacing it with a secondhand 03 car.
All in all, I would be very carefull. I'd certainly want a good warrantee on it.
ATB Steve L.