Re: claiming the tax back
"Charities get the basic rate (20%) automatically. If you are a higher rate taxpayer, you can claim the rest back for yourself in your annual tax return."
Finally! Someone posts the correct answer after many posts about Gift Aid.
Personally, I think making charity donations tax deductible is wrong, as it allows the rich to direct their taxes towards pet projects, often with side-benefits for them (think donations to opera houses, museums, etc.).