[BHPBen]

Have a search through Youtube for timing chain related videos; this might help give you some idea of what a 'failed' chain sounds like.

These engines don't seem too bad, the timing chain gets noisy but they don't fail to the extend that they lose timing and cause big internal damage. More common is the plastic guides failing and you have to go fish the bits out the sump, which sucks a little bit but a lot less than replacing bent valves. I wouldn't suggest it's a big problem, not to the same extent as say the Rover K series head gaskets (which is more of a when, not if it fails) but on modern cars, which are generally reliable machines overall, something is bound to stand out. When you think about it, any car with a timing belt or timing chain is going to need it servicing and replacing eventually in it's life cycle.

Sounds daft but most people sort of have an idea what a modern 4 cylinder should sound like, just smooth and happy, a fairly unremarkable noise. You get a gut instinct almost for if it sounds right or not. If it starts to sound more diesel like and the engine noise possesses some more old tractor like qualities start to think a little harder about it.