From Iowacompact Recycling Plastic by the Numbers
1 (polyethylene terephthatate): water and pop bottles; recycled into pillow fill.
2 (high density polyethylene): plastic milk bottles, detergent bottles; recycled into new detergent bottles.
3 (polyvinyl chloride): take-out boxes, shampoo; recycled into drainage and irrigation pipes.
4 (low-density polyethylene): Grocery bags, shrink wrap; recycled into new bags.
5 (polypropylene): Yogurt containers, bottle caps; recycled into plastic lumber.
6 (polystyrene): Packing peanuts; recycled into plastic lumber, cassette tape boxes.
7 is for “other:” includes squeezable ketchup bottles and microwavable dishes; these items cannot be recycled.
London allows items from 1, 2, 4 and 5.
Update December 1 2011: Recently London has expanded what is allowed. Items 3, 6 and 7 are now permitted, so plastics # 1,2, 3, 4, 5, 6 and 7 are allowed, along with aerosol cans and cardboard ‘cans’.