Hey guys, we have had some confirmation about the Blackberry's.
giffgaff SIM's at the moment don't support the blackberry services. You may be able to make calls or texts but any of the phones extensions (E-mail etc...) will not operate properly. We will update you as and when we get any more feedback from our senior giff-staffing team!
Apologies at this time for anyone currently affected!
I can confirm that you can install Opera Mini, gmail and other Java programs and use those instead of the BlackBerry ones, at least with a BB Pearl. There are some instructions here on how to GiffGaff your BlackBerry. It does include instructions on how to unlock your phone, which you will only need to do if it is locked to a non-O2 network. The gotcha is that you won't be able to download Java apps inside Opera Mini - you need to download them to a PC and install them from there. If you can get hold of the required files it is easy. I did need to faff a bit to install gmail, but I don't have the instructions to hand. Let me know if you get stuck and I will try and find them.