In reply to Sarah G:
Really depends on how you plan to use the phone etc
looking at my data useage in December I used 3.08GB, November 2.96GB i have unlimited data allowance and often use my phone as a portable wifi hotspot to connect my tablet etc. I use a lot of iplayer, youtube, sky go etc as I travel and stay in hotels a lot example I watched the liverpool v stoke game on my tablet tethered to my phone. Due to the unlimited data I very rarely connect my phone to wifi even at home so that pushes up data useage
also how many apps? how data intensive are they? remember they need updating from time to time and will even transmit/download locations etc. They like to use data etc so makes sure you select non automatic updating otherwise they'll eat in to your 1gb allowance.