Guys,
I think I mentioned that we happened to walk past Carpet Right and they had this offcut of a vinyl flooring. We got it for £30, and cut it up for the back of the Espace.
It's not super-duper-factory-fit, but it's enough to roll a few motorbike wheels on.
We also made a boot mat for my girlfriends Clio... and there's plenty left. I reckon the piece I've got in the Espace is about £18 if one would be picky.
It took a very long time to measure and get the holes for the seats vaguely right... Still, I'm quite pleased