Cooling problem first:
You say that after the water pump/thermostat were changed, it normally runs at 97 degrees - I reckon that's too hot anyway.
2.5TDs normally seem to run at around the 90 - 92 mark. First, I'd try another thermostat, and while it's out, ensure that there's no foreign matter etc in the recess/housing. You'll also need to add 5 litres of antifreeze, (that's 50% strength). Another common occurrence on these is a silted-up rad, but try the 'stat first.
Battery:
You could try Cybertrucker's idea, but I'd be checking-out the alternator output first to be sure the battery is actually being sufficiently charged. If you don't have access to a multi-meter, any auto-sparky should be able to do this check in a matter of minutes, so shouldn't cost much.
Try updating your profile - a helpful fellow OOF-er may well be close to hand!