did a double storey extention on mine a few years ago.my brother inlaw was a joiner to trade and used an architect to draw the plans and subby'd the rest out to collegues,i worked in b&q at the time so go a good deal on the materials,his brickie fucked off to germany after putting down the first few courses so i gave a brickie that worked for me in the q a few days holiday and me and my brother laboured for him....lol bit of roughcast and a roof later and the results were stunning.i did all the internal stuff myself.give it a go and save a few bob..