Many food packing is mixed plastic+film. Often this cannot be easily recycled and may just go for incineration even if put into a recycling bin/sack. The same may be true of plastic bottles where the top is a different plastic to the bottle. I note that the tops on plastic milk bottles have changed in the past months and all types of milk have now got white semi transparent screw tops.
I've written before on this, but I once watched the contents of a bottle bank being emptied. The public had diligently separated the glass into clear and coloured. The clear container was first lifted and emptied into the back of a truck and then coloured containers were then lifted and emptied, mixing the clear and coloured glass.
My local pavement rubbish pavement collection now allows any type of (unbroken) glass to be added to the same sack as metal and plastic for recycling.
But, my local tip no longer seems to have a dedicated plastic skip and people are instructed to put plastic into the general waste (landfill?) skip.