https://mydonate.bt.com/Used them myself back in 2012 to raise money for a children's charity. They were free back then and didn't take a %, I believe it's still the same but you'd have to check yourself.
Yeah, when I was googling I thought they look the best but it looks to me like it has to be for a registered charity if you use them and I want it to be just for an indiviual.