It's so annoying that car manufacturers have to put stuff like EGR's and DPF's on a car to reduce claimed CO2 emissions yet the cars run 10x better and are more reliable without them!
I'm not sure it's regenerating the DPF. The stuttering starts happening pretty much when the engine has "warmed up", the temp gauge hovers around 90. It's noticeable if you are going about 35mph, say, when you are stuck behind someone pondering about after about 30 seconds or so; but put your foot down, then the stuttering goes!
I also had an old 1.7DTI Corsa that did the same, but of course it had no DPF, so I'm not sure what it could be. Would a coked up inlet manifold or a faulty/dirty MAF cause these symptoms?