OP, I noticed you like Lily & Madeleine, in which case I can, without reservation, recommend The Staves, three sisters who harmonise beautifully, and The Wailin’ Jennies, a Canadian-based trio who also have sublime harmonies. You may also like, based on your short list, Paper Aeroplanes, from Wales, a duo who write sublime songs, and Rae Morris, who’s touring as part of Bombay Bicycle Club, but is recording work of her own.
Saw her a week ago in Bath, and I’m seeing Paper Aeroplanes in Bristol on Tuesday
The Staves
[video]http://www.youtube.com/watch?v=hYV0Wp0MdZ4&sns=em[/video]
The Wailin’ Jennies
[video]http://www.youtube.com/watch?v=it73sIt4Vjs&sns=em[/video]
[video]http://www.youtube.com/watch?v=YS0jBrgnidY&sns=em[/video]
Paper Aeroplanes
[video]http://www.youtube.com/watch?v=rhmVTw3ge94&sns=em[/video]
Rae Morris
I would add, that all of the above artists, and many, many, many more I’ve seen, and bought, I’ve discovered through BBC 6Music.