Geez, I thought it took me a while to find a car
Noises are difficult unless you actually hear them, bearing in mind all diesels have some kind of noise if it is then more than expected, something is wrong.
Injectors are well capable of knocking noises from just louder than normal to something that sounds like its coning out the side of the block any minute. If it's light ticking and especially from the back of the engine it could be the timing chain or tensioners of which there are several.
The mileage sounds good and it shouldn't have any noises if it's been looked after but do you want to take the risk, that soon you are going to need to start stripping it to identify exactly what it is?
Finally I don't think you can assume all B7s have no DPF, I am sure they were fitted for the last, maybe as much as 2 years or from 56 pate on approx.
Sorry to sound like a Kiljoy, could you come up with a mechanic friend who could go with you? I have even had people organise AA inspections before they buy a car (Me selling) I can understand if someone is just clueless (not suggesting you are
) it's better to pay the money and get the right car than end up with it off the road and in the Garage/large bill and so on within the first few months of ownership, I will shut up now, I am depressing myself.