It would be interesting to see why your rig's belt is tight with a 1595 belt. I found a listing via Google in that the T12030 was mentioned in a Scandinavian website as the correct part for the 300tdi- it even looked like the right bit. If you were in sydney you could try out my spare tensioner - it sounds like something else is wrong. As for greasing the fan pulley hub bearing, I've managed to wriggle a grease needle sideways past the rubber seal and inject some grease into it. A pic of the front of your engine would be good, as afaik the alternator can't be moved to take up the slack in the serpentine belt.

