...and would you like to donate £1 to charity?

[goldilocks]

i did a bit of shopping today - and in various shops at the checkout when purchasing my goods i was asked 'and would you like to donate £1 to 'X' charity?'

now...

i am big supporter of a number of charities - i think that we should all donate (however small the amount) when we can
but i do object to being asked to add an extra pound to my bill when i'm only spending £2.30 (on something completely unrelated to charity) and the fact that they were collecting was not advertised any where
how do i know the money will go to the charity?
how much of my £1 will go to the companies handling charges?
i was paying on my card, it wasn't like i was putting the odd quid into a sealed charity box - it would have been debited with my shopping.

i was in a huge queue, and i felt like a bit of an arse saying no, but we do give to charity, and to be fair payday isn't until thursday (maybe if i'd have been asked on thursday i'd feel more generous!)

so, am i an arse? i'm feeling pretty silly for saying no now. what would you have done?

(yes i know it's only a pound, but i went into about 12 shops today and i'll be going into town probably every day this week - it would add up!)