When Rupert and Julie bought a hilltop site in the Berkshire Downs, they were determined to build a house that would make the most of the countryside and stunning views. They turned to architecture firm Roderick James, which specialises in modern design and traditional timber craftsmanship. Together with architect Hugh McGann, they came up with a house of green oak and glass, built in an unusual cruciform (cross) shape.

With a plot of land in Sussex overlooking the South Downs, newly-weds Jane and Willem wanted a house that would be atmospheric and open to the countryside. Inspired by memories of America, Jane planned a New England-style gabled house with large windows to make the most of the views.

A derelict woollen mill in a Yorkshire village may not say 'modernist' to everyone. But Chris and Gill - who, fortunately, run their own specialist joinery business - saw it as the perfect opportunity to create a visionary home. They liked the traditional brick of the building and opted to keep the exterior virtually untouched. Inside, they would strip everything out and make a home of fluid spaces, based around an open-plan ground floor, an atrium and a galleried upper floor.

An isolated hilltop in the Brecon Beacons might seem an inhospitable place for a couple's first home. But Adrian and Corinna both grew up in the area, and the ruined farmhouse they chose to restore had been in Adrian's family for generations. The site's lack of mains water and electricity gave them no qualms. True, the track up the hill was often inaccessible in winter. But the landscape was beautiful and they both felt they belonged there

Helen and Mark had always dreamed of owning a Georgian house but knew they couldn't afford the genuine article. So they decided to build their own. They bought a large plot of land in Surrey, surrounded by trees, and commissioned an architect who specialised in conservation architecture to design it.

Kevin checks out an innovative housing scheme set up by a Birmingham Housing Association, which allows a group of people to build their own homes

Kevin McCloud visits a couple who are looking to build their hi-tech modern house in a quiet north London street.

Kevin McCloud visits a couple in Devon who are hoping to convert a traditional barn complete with thatched roof.

Kevin travels back to Doncaster to catch up with self-builders Michael Hird and Lindsay Harwood and their futuristic glass and steel house in a suburb of Doncaster.

Kevin McCloud revisits an innovative housing scheme in Birmingham. Just over two years ago a group of 11 men and women agreed to build, not just their own, but each other's homes.

Kevin McCloud revisits Adrian and Corrina, who decided their first home was to be a 300-year-old ruin. The former cottage is set in the inhospitable climate of the Brecon Beacons National Park.

Kevin revisits Tony and Sharon, who fell in love with a completely dilapidated Georgian home in London and undertook the challenging task of restoring it to its former glory

Kevin is in Amersham to update on a project taken on by Deborah and architect Andrew. Their venture involved designing an 'invisible' house that blended in with the surrounding reservoirs.

Kevin travels to the beautiful setting of south Devon to revisit Sue and Martin, whose dream was to create a family home using old English building techniques

'Is it a bold contemporary design or a garden shed?' John and Terri found themselves asking, halfway into their build. They had knocked down a derelict house in a beautiful rural setting and commissioned commercial architects to build them a new one. But was it too small for them, their young son and the baby on the way?

The 1930s derelict water-works Chris and Leanne 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 lived in tents and caravans in a wood in West Sussex. As a woodsman, he needed and wanted to live among the trees. But after a battle with planning he finally got permission to build himself a house with more creature comforts. He invited volunteers to help him build one by hand, from the materials growing around him.

For Philip and Angela, the build was part of a life change that had begun two years earlier. Just after their second daughter was born, Philip fell seriously ill, prompting the family to leave London and move back to his parents' village. Acquiring the site was easy, as Philip's parents owned it. Getting planning permission took longer, and a crucial factor in their success was that they would be restoring the outside of the barn and keeping the innovation hidden.

Tom and Judy 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?

After 10 years of living in a small house in east London, John and Eleni 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 in a conservation area, so the outside had to remain unchanged. Inside, however, they decided to rip out everything including walls, ceilings, floors and start again.

The old quarry stood on a slope of the Eden valley and commanded beautiful views. Local architect John Bodger designed a two-storey house that burrowed backwards into the rock and made maximum use of natural resources for light, warmth and power.

Merry's family have been Herefordshire builders for generations, so she knew that the county was rich in traditional building crafts. She and Ben decided to combine these with technology for a new house with a genuinely rural feel. Her father drew up a design that followed the traditional cottage layout while incorporating modern comforts.

Louise and Milko wanted to build the home of a lifetime. Milko's job as a well-paid City banker meant they could think big, so Louise set up her own architectural practice and they bought a disused violin factory in the heart of London's Waterloo. The crumbling building was hemmed in on all sides and had no views, but Louise had a vision of a spectacular loft-style home that would combine stunning design with utter luxury

David and Greta loved their home, a modernist structure in Surrey that they had built themselves almost 40 years ago. It was filled with things they'd chosen over the years—design classics, mementoes, David's paintings. But that house was falling apart and had to come down. Meanwhile, they had lost their hearts to a German post-and-beam house, designed by architect Peter Huf and available as a customised kit.

In November 2001, Tom and Judy demolished a bungalow and started building an infinitely more ambitious house. Designed on different levels, with glass walls and exposed steelwork, it was to be a miraculous piece of engineering, giving the couple and their two young children a beautiful, technologically advanced home. Tom appointed himself project manager—a job that proved to be more challenging than he had expected. Grand Designs 3 followed the first 16 months of the build. As Grand Designs 4 goes on air, how close is it to completion?