Must have snagged the fork guard on a stick, because when I noticed it was jammed up against wheel basically ripped off. Made a small effort to shop around for a replacement, started looking like being hard/expensive that's when me mate stepped in and said "Plastic Weld it".
He then preceeded to tell me a few tricks to doing the job.
"They use a little hot air gun, but a big soldering iron will do the same job. Clean up the edges of the work so it lines up, hold it together and run the soldering iron across the join. Work it in firstly from one side, then the otherside - so that the melted plastic is joined in the centre. Shaping your iron tip to give a 'V' will give a neat job."
Now there are many types of plastic and the plastic welders carry all the different poly* welding rods. For you, cut some little strips from somewhere else on the item as welding rods. Place them in the V and melt them in. The end job will be stronger than it was before. Oh, try not to sniff the fumes."
I followed his advice, found some areas of webbing on the back that was not critical and cut some strips off. Although I was a bit hacky (probably used to much heat and charred the weld) it really works well. There is a fine line between heating the plastic so that it is molten and burning it. Be sensible, not too much heat, but enough so that the heat pentrates into both sides of the weld, just like you were doing metal welding. The end result is very strong join - perhaps a bit messy, but on an old bike I'm more interested in function than beauty!
You know, for the rest of the time I had this bike, it never broke again :)
Plastic welded, on the left.