Hertfordshire couple Lisa and Chris dream of a child-friendly garden where they can all safely spend time together playing, growing produce and learning about nature. However, their garden is currently a ramshackle spot with a treacherous patio, a troublesome lawn, a huge concrete pad and no real character. Flo Headlam and Lee Burkhill design and build a practical, productive space to meet the needs of the family on a £3,000 budget