If they are in good condition
- Sell them.
- Give them to a charity, such as:
If they are not in good condition
Compost heap
If you have a homemade compost heap, they are ideal to use to insulate it. Just put them on top of the heap and it will help to keep the heat in.
Last resort
Take them to a Household Waste Recycling Centre (not Sowerby Bridge) and put them in a general waste skip.