Reading through some other unlrelated posts, I've noticed freddy has added a comment "polystyrene is cheap because it's crap" lol. This got me thinking. Currently our ground floor consists of a concrete base, polystyrene blocks, a sheet of DMP, and the chipboard tongue and groove floor panels sitting directly on top. There is no joists or other support for the floor. The ground floor is very uneven. I've been tempted to pull the whole lot up down to concrete so I can chip away the high spots, screed the low spots and maybe put down a self levelling compound to take care of any other smaller areas. If I ever go as far as this (quite possible as it irritates the life out of me), I'm wondering what the options are as far as insulation goes. Should I replace the polystyrene blocks or upgrade to something else. Any recommendations? Also there are air bricks at the same level as the polystyrene - just to mention.