Dave,
These are in the chassis rail, not the floorboards.
The exhaust system is mounted on the nearside. Can't see unused holes at the front although I can see one at the rear. Again adjacent to underside/rear of seat.
As on the offside, I can see the back of the interior trim.
Makes no sense to me. Just inviting water into the car interior.
I think these are factory drillings not someone getting something wrong later.
Car has only done 8000 miles with 2 non DIY owners.
Jon