I am in the middle of making a fansite for a children's programme. I was just wondering if it would be legal to post the songs played in some of the episodes, including the theme tune. Is it legal to do this? Do you have to get permission?

A lot of people do it anyway and I would think it'd be classed as fair use since you're not recreating the entire episode. I dunno, I'm probably wrong but I'd put stuff up and if a corporate lawyer asks you to take it down, take it down.

By posting the songs (song URLs, I presume), you are offering it for download. I would personally seek permission first; better safe than sorry.