I'm getting an octy L&K next week. It comes with xenon lights. Is it true that if the bulb goes it can only be replaced by the main dealer (like some vauxhalls) and it is very expensive?

No you can change them yourself but the headlight has to be removed to gain access.I would'nt worry to much they should last a lot longer than normal filament lamps.Here's hoping @ around £80 for a lamp. Having said that the extra light you get it is worth every penny.

It can be replaced by anybody who has moderate DIY skill (you need to remove 5 screws to remove the headlight unit, then 6 screws on the back to remove the rear cover of the headlight). The bulbs are not available in motor factors in the same way as normal bulbs, but you don't need to go to the dealers these days. There are plenty of online companies who can supply them. They start from about £60 for a pair (the Octy 1 takes D2S type HID bulbs). Last time I asked they were over £100 EACH from Skoda, which is why I wouldn't recommend buying from them.

Realistically the chance of you needing to change a bulb is slim, they are intended to last the lifetime of the vehicle (or a good few years at least). It's not unheard of for them to fail, but I wouldn't worry too much about it. I bought some to eliminate them when I had a fault... as it turned out, my originals were not faulty so I now have a spare set.