Had a valet clean today and found this little vw branded cap on the drivers mat on return. Can't for the life of me see where it has been knocked off. Ideas anyone?

Boot floor bung?

It is tiny, smaller than a 5p piece. Looks like a screwhole cap or similar.

It looks like a screw head cover which covers a countersunk screw in a piece of trim.  Your second picture shows the exposed part of it which would mean that whatever it fits into will have the same appearance.  It could be for a seat valence.

Yeah, I guessed as much, but have yet to find where it has come off - ho hum!

Seat base screw cover , look in front of seat below padding (vertical surface, plastic band going around the seat), I think.

I'd second dieselV6's identification - having removed those caps myself in the past it looks very similar

That is exactly what it is. What foxed me was that both my caps are missing!