Im pretty sure nearly every d21 owner has had this issue and I am about to tackle it. I found a supplier for the springs that snap in the seat. see link.
http://www.diyupholsterysupplies.com.au/page19.htm
You need the 9 gauge springs and the w clips are what I have purchased as they seem the easiest to use. I just bought 10m of the wire, when I get it I will update if it is enough or not.
http://www.diyupholsterysupplies.com.au/page19.htm
You need the 9 gauge springs and the w clips are what I have purchased as they seem the easiest to use. I just bought 10m of the wire, when I get it I will update if it is enough or not.