Charity auction on eBay
'The Grenadier Guards Regimental and Battalion Relief Charity' is registered as a charity on eBay. On the selling page, enter it in select charity and then register with MissionFish. Now select the percentage of your final sale price you wish to donate to The Colonel's Fund.
After your item sells, your donation is paid into the Fund's bank account, along with Gift Aid (if you've ticked the box).