As well as recycling your old/surplus gear, it is now possible to recycle old ski boots. Snow & Rock have six depots for this around the UK. See Recycle My Gear | Snow+Rock (snowandrock.com) for more details; there is a good video from Tecnica (a leading ski boot manufacturer) about the boot recycling near the end of the page.
GaryTodd
No recycle shops in Scotland according to website