I venture that if you put this data next to the marginal utility of money the 1% donation of the ordinary people will look way more charitable than the 8% or the super-rich.

Buffett said, rather honestly (after declaring his intention of giving away 99%) something along the lines of "don't look at me for charity advice, I never gave away a dollar I actually needed". You have to discount super-rich giving quite steeply on altruism scale.

Additional accounting note: the 8% comes from American data, so 8x is not the true ratio your 1% figure is from UK, and according to you Americans' giving is waaay more charitable. Also not known how much of the super-rich giving goes to churches as you point out.

Just to point out, we are not arguing about altruism of the super-rich, not their usefulness in a capitalist society; they are not only a necessary evil but are actually useful because of their investment profile.