fuel filter water trap?
same symptom as a mate's diesel, corners and bumps would cause a bit of water to get out of the trap and into the fuel pump (causing it to intermittently die).
as the water trap sensor was malfunctioning (jammed by gunk) there was no warning light or code being generated.
Although apparently the mk5 TDI might have an integrated water trap/fuel filter which means the whole filter needs to be changed (not a bad idea if it has had water go through it).