Aid adverts on TV

I was watching TV with DH yesterday during the daytime ( shock horror ) and noticed in every break that there was an advert for overseas aid of some description.

I wondered if anyone had knowledge of how these adverts are funded?

Having purchased TV advertising as part of my role in my working life I know how expensive it is and wondered how the cost of this type of thing is met by charities.

In discussing it with my DH we disagreed on how we thought it was done. He thinks its 'free' and donated by the TV companies. I'm convinced it comes out of donations. Im sure I read somewhere that in some cases only about 4p in the pound actually makes it to the end target due to overheads like advertising.

I'd be really interested to know if anyone has a more factual knowledge so DH and I can settle our disagreement