I then Spotted a neat modern solution that fitted our requirements really well...
A PAX wardrobe door from Ikea...
The only additional thing needed was some way of fitting it horizontally to the wall... Simple!
A pack of "Brass Mirror / Picture brackets" were ideal. the keyholes would stop the board coming off the wall easily.
So using the hinge pockets already on the rear face of the door, fix the keyhole brackets.
(NOTE - Make sure your screws are not long enough to go through the door!)
Once the brackets are on, work out the centre of the headboard and then measure the distances from the centres of each fixing. Also make a note of the distance from the top of the slot to the top edge of the door.
With these details, you can correctly mark out where you need the holes in the wall to put the screws to hang the head board on.
Hang the board and admire.