Eccentrica, thanks for the link to the Guardian jobs website. Now try looking at similar level jobs in the private sector, at those levels and for organisations which are as big and with as many staff.
I really don't understand why people expect Directors with organisations with multi million pound turnovers and huge responsibility for both employees and "clients" (for want of a better word) to be paid peanuts. There is a ridiculous expectation that charities should be run by people doing it for the love of it, but as soon as there's evidence that a charity is run unprofessionally, not surprisingly there is uproar. You simply cannot have it both ways. Charities which are spending millions of pounds of money given by the public simply have to be competitive to get good professional people. When I give money to charity, I want to know it's going to be well used, handled efficiently and by staff who are paid, across the board, a decent wage.
As for the percentage which goes on the charitable cause, 75p in the pound is ok. That link you give also shows the British Red Cross which spends 85-90p in the pound on the charitable cause. That's amazing, that's really high and a sign of a very well run charity.
"If it's such a great cause they should work for free". This simply isn't realistic. I have heard of volunteering, thank you for that. Incidentally, the costs of recruiting, training and managing volunteers would come under the overheads costs you object to.
"At least if I give money to the bloke begging on the tube I know it's going straight to him (and if he wants to spend it on heroin, special brew or fags that's his choice)."
You're happy to give money to be spent on heroin???