Yeah you'll need the extra sensors on the front and rear bumpers (think it's an extra 4 each side).@paddy6789 was looking at this from memory you will need some extra hardware but hopefully he can confirm.
But you'll also need some way of putting an indication light on the wing mirror. Unfortunately the indicator on the wing mirror will most likely be on a series circuit so if you have that light up when someone is in the blind spot, all the indicators on that side of the car would also light up.
The Ateca has it, so the sensors and wiring can now all be bought as genuine parts. But the Ateca has the indication in the wing mirror glass, and it's a different shape to the Leon glass my idea is to buy a small LED or a cluster of 4 LEDs and have them on the bottom of the wing mirror housing. Some people have fitted an interior light to the side pillar.