When Monty Ravenscroft and Clare Loewe began looking for a house to buy in London they soon realised that the only affordable option was to build one themselves. They snapped up a dirt cheap slither of land in Peckham at an auction only to be told it was too small to put a house on. Undeterred, three years ago, engineering whiz Monty began building an extraordinary experimental bungalow that filled the site to bursting point.

When lawyers Jeremy and Louise Brown walked into Upthorpe Farm in Gloucester, they couldn't believe their eyes. It was like stepping back in time. Apart from a few minor alterations, the Grade II listed 16th-century farmhouse had barely been touched for over 400 years and was completely unmodernised. There were original beams and doorways, original paint and plaster and a hay loft. Now that they've purchased the property their ambitious design plan is to bring the farmhouse into the 21st century, blending the original historic features with modern simplicity and luxury. Kevin watches on intrigued as they tackle the challenge of reconciling the very old and the very contemporary.

John Cadney and Marnie Moon have never had a permanent home. For 16 years they've camped on land owned by Marnie's parents because they could never afford to buy a house in the area where they live. So John, a carpenter, rolled his sleeves up and decided to build a house for his family with his bare hands. After much searching for the right kind of house they settled on an environmentally friendly four-bedroom log cabin. The whole thing was imported from Finland as hundreds of pre-cut bits of wood. All John had to do is figure out how it all fits together!

For the last 20 years, Pat Becker has been living in a large Georgian family house overlooking the sea in Devon. Now that her family have flown the nest and the house has grown too big for her, she's decided to build a new home at the bottom of the garden. Shaped like a curvy seashell, the new house has concrete and polystyrene walls, which spiral down from the central staircase. Her architect has promised it will take only six months to build but constructing a round house is never straightforward!

This is Belfast, one of the great cities of the industrial revolution, and home to Thomas and Dervla O’Hare. They’ve lived here for 18 years, and although they still love their tiny cottage for its compactness, they’re about to build something much, much bigger. They’re building a 21st century answer to the Roman villa, with a copper roof, glass and concrete walls and vast amounts of living space all arranged around a central courtyard.

Kevin McCloud meets Julie and Mark Veysey, whose Grand Design is a stunning Miami-style beach house on a beachfront plot overlooking the south Devon coast. Julie and Mark have had several holidays in Miami, and Julie wanted to recreate the outdoor beachfront lifestyle back in England, living in a house full of light and sun, within easy reach of the waves.

Andrew and Lowri Davies embark on a project to build an environmentally friendly farmhouse in rural Wales. Encouraged by their architect, they opt for some state-of-the-art experimental building materials; but do their builders know how to use them?

As the budget spirals out of control, they find it increasingly difficult to balance the budget with their desire for a sustainable home.

Kevin revisits Andrew and Lowri Davies who embarked on a project to build an environmentally friendly farmhouse in rural Wales. Encouraged by their architect, they opt for some state-of-the-art experimental building materials; but do their builders know how to use them?

As the budget spirals out of control, they find it increasingly difficult to balance the budget with their desire for a sustainable home.

Engineering whiz Monty Ravenscroft built an extraordinary experimental home in Peckham. Kevin returns to see how it suits Monty and his partner now they have a child.

Kevin catches up with Thomas and Dervla O'Hare who built a spectacular home on a hillside in Belfast.