What PAYG network is the best for a Blackberry 9300?

I'll be getting a Pay as You Go Blackberry 9300 in a couple weeks and I need help choosing between providers (T-Mobile, Orange, Vodafone or O2). I'm currently on Orange Canary but I don't chat much on my phone and only text occasionally. I'm more concerned about Internet Tariffs for BBM. What network/call plan would be the best for me? (Not looking to spend more than �10 a month tho!! :P )