[(Dave)]

I've been getting an intermittent slight rattle on my 308 sport which I'm fairy sure is the chain but only now and then on cold starts but fine when engine warm. like you I'm not willing to spend that kind of money at least not yet so I've bought the latest revision chain tensioner and waiting to fit that, as apparently its often just a failing tensioner causing the rattle. But the chain can't be ruled out until its checked for any stretch and if out of tolerance would need replacing.
I was hoping someone else had done the replacement tensioner job and could advise on a couple of things, but it looks like I'm just going have to do the straight swop of parts and see if it cures the noise. I don't have any other problems fault codes etc.
Your best thing is if your going to keep the car and it has no chain rattle, is to service regularly using recommended oil and never letting it get to low, keeping well topped up and it could be fine for years. But replacing the tensioner (about £40 for the part) is also a good precaution to have done sometime if you decide to keep your car.