The front bumper differences between K1's that you discuss (some have slats some have mesh) are due to them being added on after factory. K1's from factory have the black fins in the front bumper, Cupra's that have left the factory as Cupras and then had the K1 body kit and badges added after (possibly by dealer) will have kind of a mesh instead of the fins in the front bumper. So the speed Blue K1 in this article has had the k1 bodykit and badge fitted after leaving the factory as a Cupra.
Love Speed Blue!! Enjoy it!
A Blue Austin Mini City 1000 which looked like a Cooper when I finnished the project. That was many moons ago LOL.
I thought the front bumper without the slats at the side is the revised one. So yes K1s will have the slats but so will some leons with the aero front will have thye same bumper as the K1 until Seat changed the side vents to grills.