I did not know what was going on in the inside of the back rest, so it was interesting to remove the fabric cover and see the construction.
The webbing and foam needed replacing, I followed the instructions in a book called House Proud by Danielle Proud, which worked a treat.
My husband helped me stretch and attach the herringbone webbing with upholstery tacks.
I then tacked on a piece of hessian over the webbing. The 1" foam was laid down on top of that and then lightweight batting was stretched down on top of the foam and stapled into place to hold down the foam.
The cover was just pulled down tight over the back rest frame and stapled firmly into place.
I made a box cushion to cover the new 3" foam seat pad, that has a zip fastening at the back
Obligatory gratuitous shots:
I am really proud of our efforts here. My husband still has to sand and varnish the wood, but I've done my side of the bargain. I bought all the webbing and upholstery supplies from ebay shops, and the foam locally. Now that I know we have sorted out the structure, I wouldn't be worried about changing the fabric again. Any questions, please ask.