Grand Designs - Season 3

Kevin McCloud is in Cambridgeshire, where John and Terri Westlake intend to knock down a derelict house and commission commercial architects to build them a new one.

The 1930s derelict water works Chris Jones and Leanne Smith fell in love with was huge and its design had clearly been inspired by Gilbert Scott's Bankside power station, now better known as the Tate Modern. But nothing would deter the couple. 'We looked at it,' said Chris, 'and saw our home.'

For 10 years, Ben Law lived in tents and caravans in a wood in West Sussex. As a woodsman, he needed and wanted to live among the trees, but now he wants a house for some creature comforts. Ben has invited volunteers to help him build a sustainable house by hand, from the materials growing around him.

Philip and Angela Traill set out to convert a 150-year-old barn near Surrey. The barn is grade two listed which means they have to keep the outside intact but are free to do what they please on the inside. They didn't want to do another typical barn conversion, so they decided to build their "house" inside instead. A helical stairway leads to a suspended curved walkway, with master bedroom on one side and the children bedrooms on the other. The kitchen is in an adjacent stable block, which was integrated into the main building. The house is also packed with computer wiring a central stereo system and ambient lighting system consisting of 188 lights. Everywhere you look curves interplay with straight lines. The result is a beautiful mixture of new and old, exquisitely finished in detail.

Tom and Judy Perry wanted more than just a home for themselves and their two children. On a site of outstanding natural beauty in Buckinghamshire, they set out to build an ambitious house – a symphony of angles, glass walls and exposed steel, with a dramatic inverted roof. Tom made himself site manager and main contractor. He had no experience but he liked a challenge – and, after all, how difficult could it be? And it turns out to be very difficult.

After 10 years of living in a small house in east London, John Flood and Eleni Skordaki hankered after modern, open-plan living. They didn't want to move, so they decided to give their Victorian terrace home a radical redesign. The house was situated in a conservation area, so the outside had to remain unchanged. However, inside they decided to rip out everything; walls, ceilings, floors, and start completely a fresh.

Helen Gould and Phil Reddy wanted their home to make the most of spectacular views, but they also wanted it to be ecologically friendly. Their solution was to build an earth-sheltered home, with most of the house built into the hillside.

Merry's family have been Herefordshire builders for generations, so she knew that the county was rich in traditional building crafts. She and Ben Albright decided to combine these with technology for a new house with a genuinely rural feel.

Kevin McCloud catches up with Rupert and Julie Upton. The three-year build on the picturesque slopes of the Berkshire Downs was wracked with hold-ups, set-backs and spiralling costs but the gardens have now been landscaped, and the timber frame has aged in colour from honey to silver as the property settles down into its outstanding rural setting.

Kevin McCloud catches up with Sarah Wigglesworth and Jeremy Till, who constructed their experimental central London house out of straw bales, springs, cloth cladding and sandbags. They laid themselves on the line, both professionally and personally, as their build slowly advanced from one architectural style to the next. Kevin returns to this award-winning house to find out whether it is well and truly finished.

Kevin McCloud revisits a couple who converted a disused electricity substation in Sunderland into a four-bedroom family home, armed with just £50,000 and ideas from a book about Moroccan interiors. Despite a number of setbacks, Anne and Richard Curtis created a living space which, three years later, has had a sumptuous rooftop garden added to it.

Kevin McCloud catches up on retired couple Denys and Marjorie Randolph, who had decided to embark on their final building project, a brand new, green oak, barn-style house.