IIRC the DPF was pretty much an essential requirement in order to meet EU5 Emissions regulations, though they may have been fitted to some vehicles earlier.

The regulations were introduced in late 2009 and all cars sold after Jan 1 2011 had to comply with EU5. Being registered prior to 1/1/2011 the Fiesta in question doesn't have to have a DPF fitted, and NCT will probably only care if one was fitted from the factory and removed - similar to their take on cats.

So, from a purchasing point of view, happy days, one less thing to go wrong. The downside is probably that the emissions on the car are probably higher than one with the DPF fitted and EU5 compliant and so may be subject to slightly higher road tax.