I haven't been able to find any instructions whatsoever, on how to make a head support cushion (head hugger) for a car seat.
I figured that I had fabric, I had wadding and I have a sewing machine - how hard can it be to make one!
I guess the end result speaks for itself - better than nothing but not really good enough!
I could have made it better. I was rushing, I was frazzled and I was making it up as I went along.
I thought I would post the instructions on how I made it just incase somebody can improve on it and come up with a reasonable one! LOL
Costs were negligable, an old pillowcase in the appropriate colour and some left over 6oz wadding.
Firstly make a paper template the fits inside the carseat, mark on the position of the shoulder straps. Make sure that when the straps are in the lowest position that the template does not cover the crotch strap.
Double up the fabric and mark out the shape of the car seat and positioning of the shoulder straps.
Cut out the fabric 6cm wider around the sides and the top, and 1 cm wider at the base.
Lay the fabric on a piece of 6oz wadding and cut the wadding to the same size as the fabric.
Turn over the top layer of fabric so that the pencil makrs are not visible and pin both layers of fabric to the wadding.
Stitch around the curved edge and turn the right way out (so that there is fabric on both sides of the wadding!
Stitch around the pencil mark from the paper template.
Cut a strip of fabric 4 cm wide and 2 cm longer than the cushion.
Iron 1cm in at each end. Then iron the strip in half lengthwise, then iron in the raw edge towards the middle of the strip so that you have a neat edge for sewing.
Pin the edging strip over the bottom edge of the cushion, enclosing bothe layers of fabric and the wadding sandwiched between them. Pin and stitch in place.
Cut a strip of wadding long enough to go all the way around the curved edge of the cushion and about 8cm wide. Roll the wadding into a sausage.
Fold the cushioned curved edge of the cushion in toward the centre, using the stitched line as your guide for the outside edge. Pin it down and insert the wadding sausage into the gap.
Stitch the stuffed edging down and then make two large buttonholes over the pencil markings for the shoulder harness.
It was at this point I realised that I hadn't left enough room for the babies head! 
So I added a couple more "button holes" slightly further down, so that the support cushion could accomodate both the harness and the babies' head! I'm hoping that with the shoulder cushions it will do - chances are it will only be used once, when I need to get home from the hospital after giving birth!