So basically some of the tariffs I've been offered with no data are pointless for a BB if you want to use BBM an email?

There's a cheap O2 one with 50mins, 250txts, 100Mb data for £13.50. Is this enough data for BB though? My iPhone contract I get unlimited and browse a lot bit checked and am using about 750-1Gb month. My wife & daughter won't use anything like this though, if fact probably won't use internet as such