Now here's a thing.
The Pluriel actually seemed different when I test drove it.
I said to myself, "this must just be psychological", but it isn't the first timing belt change I have done by a long chalk. And never before has one seemed quieter and a tiny bit sharper. TBH they just drove exactly the same.
However, when I took the old tensioner off, the indicator pointer was pointing way off towards "relaxed", didn't think much of that at the time.
So I took the old one into the garage and "fitted" it using the vice, a bolt and nut to simulate the spindle and nut that holds it in place, plus the handle of a spanner to lock the adjuster base plate in place. But could I adjust it as I ought to have been able to? Could I flip. You put an allen key in a shaped hole on a plate on top of it, relax the nut a bit and use the hex hole to turn the plate, but there seemed to be no connection at all between this and the sprung adjuster, although the spring was deffo not bust in fact it was really strong and it took a lot of ingenuity and effort to make the two halves of the adjuster move to the "locked" position that the new one came in, with a metal pin holding it like that.
So I came to the conclusion that some connection between the top plate and the bottom one had simply just "gone".
Which would mean that for Lord knows how long it has been running with the tensioner on its softest position. Yet it ran fine and the timing belt that came off looked as if it had only been fitted a week ago. I'm beginning to wonder if the faulty part was fitted right at the beginning because when we bought it it had only done 10k miles and had only one service stamp in the book, the very first sort of "run in" service, not a proper one.
Still not sure about all this.
Weird.