Several UK charities take used stamps so they can sell them to collectors. The Used Stamps for Charity webpage lists charities, gives addresses to send stamps to and also tells you when they last confirmed the address.
The charity Lepra accepts used stamps to fund their work fighting leprosy in Mozambique, Bangladesh and India. They told the Pass It On Wiki: "We raise somewhere between £5,000 and £10,000 a year through the sale of used stamps, so we really do appreciate it."
You can post them to:
Most recently checked: December 2018