In O2 stores you can now choose a contract of £35pm or greater and a free Blackberry handset and with the use of the free choice of one inclusive Bolt On. The Bolt Ons that can be chosen now include the Unlimited Blackberry Internet Service (as long as you have a Blackberry and not to put Blackberry on a non-Blackberry device).
This is not available on-line or over the phone. (I rang them and they didn't know what I was on about!). Also, it's not available to existing Blackberry customers, but you can swap to the bolt on upgrade.
Here's a link for a news article on it:http://www.mobilenewscwp.co.uk/News/61219/o2_adds_blackberry_unlimited_bolton.html
Hope I've got this right. However, I'd wait until the new Blackberry Bold (9000) comes out in the next 3 months.