i would imagine that the council (who are the current "owners") have a right to say which properties casn be sold, and which cannot, and i'm sure they are protectd in law (although i have no basis for beliving this, other than the fact i think they ought to be)
personally, i think it's a good idea that bungalows are not sold, because where are they going to put pople in the future who cnt manage houses and flats? Imagine if your parents were disabled, and had to live in a 3rd floor flat that they couldn't even get out of, but couldnt be re housed bcause because there were no bungalows left? Actually, having said all of that, i dont really agree with "right to buy" anyway, as it completely reduces the housing stock.your parents might not even be in a council bungalow now if right to buy had come along earlier... there simply woulddn't be anywhere left to put them! now i know all of that dosent help you at all, and wasn't strictly what you were asking, but dont get cross with me please! I'm just asking you to consider it from another point of view, before taxpayers money is wasted going through a tribunal, or your parents waste what money they have on it. they will still be able to lave an inheritance, just in money, not bricks and mortar