Tracy Fox and husband Steve want to build an 'urban shed' out of industrial materials in an old milk yard in south east London. But the choice of unorthodox materials proves challenging and costly.The build will feature two studios, three bedrooms and a double height space with walkway, with materials including corrugated cement fibre board and 20 foot panels of polycarbonate sheeting.Work on the build stalls until they meet Romas and Remi, a young firm of builders, who boldly decide to take on the challenge of building it for just pounds 300k.