Hi Steve, I would change the chain, tensioner and sprockets, I believe they're available as a kit. I haven't checked cost of parts as OEM but, non OEM I would hazard a guess about £120. It goes without saying on this kind of thing I always say go OEM. If the chain does break as it has in these three cases the damage at high speed or low speed would lock your engine as if it were seized thereby locking your wheels but you'll be able to coast along to a stop if you put it into Neutral. If the chain falls into the sump then I predict the oil light will come on also there will likely be vibrations as the balance shaft will stop.
I forgot to mention my TDi I bought about 3 years ago, with the exact same fault at 110k. I suppose the lifetime of this tension is down to the oil changes and quality of oils used, as well as how it's been driven along it's life. I am just advising and not scaremongering anyone, it's up to you all to take care of this as I see this problem happening more in the near future.
If you're 'lucky' so to speak, then you'll hear clattering noises which will signal the chain is loose.
Also if you're due a cambelt change, I'd suggest to get it done at same time as it'll be cheaper that way.
Thank you Steve, I'm sure everyone also appreciates your services as well.
Sarge