Most of the charity shops won't take them but I have listed mine on the "freebies" section of Gumtree and they have always gone. Someone very grateful will probably pick them up from you. Likewise on mattresses if they are in clean condition. I've successfully got rid of mine that way to people in need. It's a good way of re-cycling a lot of things if they are in good condition - I have given away garden equipment, old TV's that still work, baby equipment, bedding, furniture that the charity shops won't take, small electrical goods like kettles and toasters that still work, etc etc.