Vodafone help!

[dazed57]

I originally posted this question in How it works before realising I should have put it here! (Sorry!)

I have been given a second hand Blackberry 8310 curve and my PAYG sim card works fine in it for texts and calls, but I'd really like to use all the nice apps on it (twitter, facebook etc) Before I go into the vodafone shop and get sold everything under the sun does anyone know the cheapest tariff you can get for a blackberry?