Windows :: Managing A Small Data Allowance?

i have recently switched from an expensive iphone contract down to a cheaper contract with a lumia 800 (for budget reasons). the main problem i will be facing is managing a small monthly allowance of data and wanted some advice.on my old contract i had 700mb a month which i regulary went over (despite having wifi at home) and this contract only has 250mb a month, quite a step down! my main qeustion is how much do you really get for 250mb? obviously having my people section linked with facebook and twitter etc would eat data when it updates so i don't have any of that setup. are there any standard apps that use data without you realizing that i should remove or turn off? how much browsing and perhaps Internet streaming you could get ut of 250mb?i have to make this work and change my ways of browsing the net out and about and needlessly watching videos on 3g as i can no longer afford not to.