Any of the albums mentioned would be a good choice; I also thought last year's "The Life Pursuit" was wonderful. "Another Sunny Day" is one of the best pop singles for eons, IMO.
AllYouNeedIsMoz, what song did you hear that got you interested in the band?
Also, I don't mean to get the thread off track (this is sorta related) but if you like Belle & Sebastian, you might also enjoy another Scottish band called Camera Obscura. When I heard their song "Suspended From Class" I actually thought it was Belle with one of the girls singing. Anyway, I've really gotten into Camera Obscura since checking out a couple of their albums -- their most recent is "Let's Get Out of this Country". The title track is wonderful, as is "Lloyd, I'm Ready to Be Heartbroken," a sort of answer song to Lloyd Cole's "Are You Ready To Be Heartbroken?" from days of yore...