Hello Fil,
I would think that your problem would be the injector seals leaking as you suggested. Although I haven't done any on a VW yet, we have had several on Landrover TD5's with unit injectors.I would get them done as soon as possible, because there is a risk that the engine could run on the overfilled oil/fuel in the sump, causing it to rev beyond control.
Hope this helps, Regards,Andrew