They would contaminate the entire
Odds are pretty high that you cannot simply bring this glass to your local recycling plant. Most recycling centres in London do not accept treated glass, such as that which is used in light bulbs, mirrors, and windows. This is because the additives that are used in the manufacturing of these products, including the fibres that are added to strengthen or block UV light in window glass, are not accepted by most plants. They would contaminate the entire load of regular recyclable glass, much of which goes towards making packages for edible products. This means that much of the window glass London residents need to be rid of ends up in the bin.