Hallo Klaus, the converter kits are used for travelling from the UK to Europe, or vice versa. I've found the standard ones for H4/H7 headlights, but none for the Xenon lights that my Altea already has.
Basically it's the old
sticker method, "Scheinwerferabkleben".
BTW, I also checked the german Altea site as well as the Leon forum. Using both a lot and very helpfull indeed for my old Leon TS TDI.