Info about O2 UK PAYG Blackberry Roaming:
As an O2 UK Pay & Go Blackberry customer you will receive 10MB free Blackberry data usage per day whilst roaming. This means you can use email, browsing (as long as you use the Blackberry connection), and blackberry features such as blackberry messaging and facebook.
Using O2 Active or browsing where you use the O2 Data connection (such as O2 Active, streaming data or internet tethering and third party applications) you will be charged the normal roaming rate for data use.
Please note: Data Usage beyond the 10MB free allowance per day whilst roaming will result in removal of your Blackberry services; after which only re-purchasing the Blackberry Bolt On or topping up a minimum of £15 if on the Blackberry tariff will re-activate your Blackberry service.
I am a Pay & Go customer what services do I get charged for if I go abroad with my BlackBerry? - Support - O2