To update you all. I have finally finished the headrests on the R & R bed.
I managed to find some 16 mm (5/8") square steel tube in B & Q that was the same size as the original seat back.
I welded at an angle so the rear top edge of the seat back could still rest on the plastic moulding over the engine bay. Originally I was going to use some second hand headrest guides from old front seat but they are too big, so I had to find a way of holding the headrests in place but they had to be easily removable when the bead folded down.
Because I welded the tubes at an angle I had to cut slots into the back ofthe seat, to strengthen the seat back I put some addition tabs on the frame to pop rivet the seat back onto (that was the way it was originally fitted)
I welded some M8 nuts in place and then fitted some detent screws (M8 grub screws with a springloaded plunger in the end that clicks into the grooves on the back of the rods that mount the headrests.
Any I an sure the photos will explain.
I feel much happied not that the kids have head rests in the back.
The bit that took the longest was stripping the powder coating off the frame prior to painting it, a couple of hours scraping and sanding