[Closed] Car warranty

At the beginning of october the wife bought a V. low mileage 2 year old Merc from the local dealer.
We collected it last thing on a friday evening and drove home, halfway home, as I was driving, I spotted a stone chip in the windscreen, right in my eyeline, so we phoned them first thing Saturday morning and they agreed to repair it.
Great.

Now I've found that one of the LED's on the high rise brake light doesn't work, the other dozen or so do, just one LED in the middle. I've just priced one up and it's £82+vat (supplied only) which is quite a bit more than a single bulb which I'd be happy to suck up the cost of.

Can I go back to them and say fix it or is it a consumable part?
LED's are meant to last ages though aren't they?.