Toorak home with council-approved plans is drawing buyers keen to turn it into one of the suburb’s next multimillion-dollar masterpieces — all without the price tag of a finished home.

A white stucco megamansion in Surrey, England, is making a splash not only for its stunning new look — but also its big price.

It took more than two decades for owners Sue Charman and Martin Whitlock to complete restoration of Green Dragon Barn, ...