Duvets. Yes, duvets as wall insulation. The fillings of man-made ones are chemically treated polyester fibres to make them fire-safe so that they smoulder and melt before becoming combustible. The local tip is in the middle of studentland and has a container specifically for duvets. Winner.
Another is roof tiles made from paper and hard to recycle plastics. Paper can only be recycled a few times before the fibres become so short as to be useless. Black plastic food trays are difficult to recycle as their colour contaminates now products, so mix the two. Blend the two in a solvent then roll it out und put under a heated press, same way as circuit boards are made, chop them to size and you have roof tiles. They are waterproof and insulating.
And finally - chewing gum. The days are long gone since the natural gum, chicle, was used to make the stuff. The modern version is a mix of polymers and plasticizers... plastic. It is now being used to make coloured Wellies, fishermen's waders and waterproof ponchos, and that keeps the streets clean.
All UK ideas for making money out of waste, or as we say in Yorkshire "where their's muck there's brass" and there is.