I've been approached by the uk company TwoFour because of a video I posted on YouTube a little over a year ago. They want to use it for a show they are doing for the Discovery Channel, called What Happened Next? I've never sold the rights to a video before, nor was it my intention when I took the footage. It's just a clip I took while on vacation. I'd like some advice on negotiating a price for this. In the message they said "Discovery requires that the footage that we use is cleared for all media, 10 years, world wide".