So I got John Lewis out to have a look at it. The inspector said that because it's been there a while the vinyl might have memory and never be completely flat now. There's another less obvious ripple near that one across the width of the floor, and another in front of the washing machine.
The inspector said that for the sake of a £95 call out fee he'd be inclined to see if they can re-fit it.
It's not the money I'm worried about, it's the major hassle of moving the F/freezer and the world's heaviest washing machine (Miele), if I end up having to do that twice I'll be well hacked off.
I could of course just get them to fit a new sheet of vinyl, but there's no guarantee the same thing won't happen to that and I'll still have to move everything a 2nd time.
I then thought about LVT like Karndean/Amtico but they seem very thin and I'm not convinced how well they will cope with the flexibilty of a wooden floor underneath (it's been screeded but it squeaks).
No idea what to do