As I understand it - eBay have a pretty clear & strict charities policy. eBay_UK dont appear to have suc a specific one - but as a subsiduary of eBay_com they surely come under same policy - which is that the listings have to be done through missionfish.
Isnt nice to feel alienated that you cant post a few items to raise some funds - however there is nothing stopping you listing the items & donating the funds anyway... You just cant say that that is what you are doing with the proceeds from the sale within the auction!

As harsh as it seems - policy is actually designed to protect people wishing to make donations by making it harder for scam-artists to set up an auction saying that something is for charity & then not giving the money.
You have to say up front what percentage of the listings final amount is then donated to charity & that amount then goes to missionfish, with any remainder (non 100%$ donations!) going to yourself...
It also stops inappropriate items being listed, as a rep. from the charity has to approve the item - idea being to stop a collection of zippo lighters being auctioned to raise funds for cancer-research etc (if the charity objects to the relevant listing of course).