Sounds like a pretty sound example overall and you've done a lot to it. IP shaft seal is not too hard to change, worst part is R&R'ing the pump off and back onto the motor -- if you've done the headgasket I'm sure that will be a cakewalk for you.
A 945 TD with a manual trans would be a prize to acquire on these shores, especially one with relatively low miles and in good shape on the inside. Amazing how cheap good used cars are in the UK... you're asking about 500 bucks for something that would probably sell instantly for at least 5 times that over here! I guess it's the MOT issue that makes old stuff expensive to keep around, right?
If you let it go, hope it ends up with someone who will keep it on the road.
