The 1.3 CDTi engine (much like the entire Corsa D) is a Fiat. It's by far the most-manufactured small diesel worldwide, so there are more people out there who've had problems. The biggest number of problems usually come not from the engine itself but ancillaries added on like the DPF or the turbo. Mostly city running with a weekly blat on the A roads is just about on the cusp of "you'll probably be ok with the diesel" but they really don't like pootling short journeys with lots of stopping and starting.
OTOH, the D, like a lot of post-2005 cars, is a damn heavy supermini and I found the 1.2 annoyingly unleggy. My Modus (pumped up Clio3) is a 1.4 and that's acceptable without being nippy and I really wouldn't want the 75hp 1.2 version. Based on my exp (I hired a lot of 1.2 petrol superminis in Malaga over the years; Fiestas, Corsas, Puntos etc) make sure that a naturally aspirated 1.2 has acceptable legs before buying.
You might wish you'd got a 1.4 or, better still, something like Renault's 1.2TCe because the little turbo really did give it the highway zip as well as the docile performance and mpg in town.