No one on our street has done this. There must be a reason, we assume it's not possible. Our loft is big but fairly low height. Still, a room seems plausible. We will have to move if we can't extend up, so whilst it's unlikely we can extend, I want to find out for sure as cheaply as possible. Where do I start this process! With an architect?,a loft extension company? Putting something to Southwark? If you know, please advise. Much appreciated.