"He's more Devonshire than I am now," laughs Caroline. "He loves it."
With a background in property development and furniture design, the couple were keen to apply their talents to a home of their own, having worked for residential and private clients in London. They cut their teeth on a huge hospital wing, part of a former Devonshire mental institution, which the developer sold on to them before starting his own section. The Bantocks camped out with Caroline's parents while working on it. They completed the project for £120,000 and sold it on for £250,000. They were ready for the next challenge: Garden House, at Haytor on Dartmoor.
Two factors were crucial to the initial choice of site and design. The plot of land within the National Park already had a building on it, so redevelopment was permitted. The dilapidated old asbestos-lined bungalow had been thrown up after the war and had outlived its usefulness, but it did sit in the most wonderful moorland gardens, full of camellias, heathers and ferns. It wasn't hard to demolish.
"We just leaned on it and pushed," recalls Caroline. "We couldn't believe we'd found such a beautiful spot."
The second X-factor was finding architect Roderick James, who specialises in oak frame design. The Bantocks had spotted his work on a TV property show and decided their next home had to be a Carpenter Oak production. They scribbled down his name at the end of the show. Then they discovered he too was based in Devon; it had to be fate.
Sensitive to what they were allowed to do within the National Park, and keen to build a home sympathetic to the wild nature of the area, they worked closely with James on all aspects of the design. The structure is oak faced, with glass and granite used to blend in while providing light, and reclaimed Delabole slate on the roof. Steel sheet metal was used on top of the porch, better, say the owners, than the traditional lead or copper and fading to match the silvery grey of the oak.
The whole project took two years to complete. Unlike some self-builders, the Bantocks decided against living in a caravan on site during construction. As they point out with some justification, Dartmoor in winter is not the place for caravanning. They went back to live with Caroline's family, but were very hands-on as their own project managers, being there every day.
The attention to detail is impressive. Determined to make the house as seam-free as possible, all evidence of the workings have been hidden. The heating is underfloor, there are no thermostats on the wall. Each area is zoned and the temperature controlled by handheld units which are tucked behind picture frames. What you see when you walk in the room, is what the Bantocks intend you to see. Only an interior designer could put three small logs and a bowl of heather on a dining table and make it look perfectly reasonable.
There are also two kitchens, the main one an immaculate, theatrically lit area with a black Aga, in a corner of the 31ft open plan living/dining room. The thinking was it was wasteful to have a dining room which might be used just one day a year and then closed off. That being the case, the on-show kitchen had to look uncluttered and perfect. A second, more workmanlike kitchen - much too smart to be described as a utility room - was built on the side, with steam, convection and microwave ovens, big fridge-freezer, plus a second dishwasher, something every country home should have.
"With open plan you have to be so disciplined, so you need other areas you can spill on to," says Caroline.
The house has decking to two sides, with doors which open out for summer living. It has a high vaulted oak ceiling, but the feeling of womb-like warmth in the lower living area is enhanced by a circular wood burning stove. It's overlooked by a galleried sitting room on the first floor, its Juliet balcony echoed by a partner off the main bedroom on the opposite side. A second, along with a very much smaller third bedroom, is on the ground floor. The interior design is comfortable contemporary, with the kind of bathrooms you'd expect in the best boutique country hotels, right down to a touch of product placement - Molton Brown handwash by the basin. Everything has been sourced using the contacts the Bantocks have built up in their business.
"It was all so carefully chosen. We knew exactly what we wanted, it all fitted to the millimetre. You could say we are perfectionists."
Now with an 11-month-old daughter, Clem, the Bantocks are selling up and have their sights set on a renovation project, still in Devon.
Get the spec
What's for sale: three bedroom, oak-framed house with a galleried sitting room, vaulted ceilings, a study, two kitchens, and landscaped gardens on Dartmoor National Park.
Serious kit: Impeccable interior design, parking for 10 cars, productive kitchen garden, young orchard, boundaries protected by an invisible dog fence.
Buy it: £875,000. Jackson-Stops & Staff: 01392 214222.