Recently changed my vac pump, but on a 300TDi. The leak was from the end cap that is riveted in place. Oil was getting everywhere and being thrown all along the back and side of the engine by the air from the cooling fan.
Quite difficult to trace at first but eventually sussed it. Hoped the end cap was bolted and would just be a gasket job but its replace the entire unit I'm afraid if that's where the leak is from. Apparantly they will leak for ever without causing trouble but best sorted I'm sure.
300 TDi has an oblong flange and gasket, with six bolts, bottom ones are a bit awkward to get at. Engine needs setting up in correct position on cam so plunger is not loaded when refitting. Bolts are not long enough to pull the pump in if not.
200 TDi vac punp is geared and I don't think engine position is important . . . but I may be wrong on that.
Give all the oily bits a good gunking, wash clean, then get out for a run, wipe finger along under joint where pump end cap is riveted and if you get an oil mess, that's most likely the problem.
If it's simply the flange/block interface gasket. Should be able to replace that for a few quid
Just short of 100 quid to fix mine :( but it don't leave oily puddles all over the drive now - SWMBO was well impressed :lol: