I can't find anything on Google, it's as if it didn't exist.
It was cardboard boards, quite big, probably bigger than A3 size. They had pictures on of different things that you could build and plastic clips to put them together.
You could build a Wendy House, a kitchen, a boat, a car. Big enough to sit in and play in. The plastic clips had hinges so that you could open the door on whatever you'd built.
No idea what they were called, does anyone know?