Would 100mb be enough data for me, i'll only be using it for sending abd receving emails, occasional web browse perhaps once a day for a few mins.

100Mb a month is for very light use. Be wary of attachments and video would eat it up in no time.

It depends on the BlackBerry. If it's an older model and mostly does text email you might be OK, but if it's a newer version with a webkit browser you could burn through it pretty quickly.

If your BB has wi-fi, make sure you use wi-fi wherever you can, that will take the load off a bit.

100 mb? Walk away, don't even bother with it, you'll go over that with low usage unless you're honestly only going to use it once or twice a week at the very most.

The Blackberry.Net APN that is used on all Blackberrys is exceptionally data efficient to give you an idea of how good it is you can run about 4 Blackberry devices for every iPhone in use.....it essentially uses about a quarter of the data.

Even with Webkit everything is still sent through Blackberry.Net proxy and compressed, removes bits of information the sites doesn't need or the device can't understand.

If you use wifi when at home, then 100mb on a blackberry is probably quite sufficient, I get through around 89mb a month and I use my device quite heavily.