I found this site with her voiceover work. There are two commercials you can listen to. They describe her voice as "fresh, playful and reassuring".
Personally, though, I do not like her voice at all... It's a visceral thing, I just can't make myself like it. image It sounds so screechy to me.

http://gordonandfrench.co.uk/home/artist-profile/anne-marie-duff/