In this scenario they don't pay for the plastic. They receive £30 and a tonne of plastic.
The government might as well be part of such fraud too? What do they care, if the plastics is not actually recycled.
But if they cay say to the voters, "Now we're recycling all plastics", then, some more votes, they'll get, in the next elections? (Maybe just a few more votes, if most voters also don't care)