I think you need to speak to your HR department. I work for the NHS and am also subject to the public sector pay freeze but I've been in the job a while so am at the top of my band, so no rise for me at all for the past couple of years. However, there are people on my team who have only been with us a couple of years and they are still getting their band increments, they haven't stopped - and anyone earning less than £21K is getting a flat £250 increment this year.
I wouldn't count on the freeze ending in May 2012, the financial year ends in March 2012 and it may all depend on the state of the public purse by then, any extension of the current freeze will have to be renegotiated. Your HR department will be able to tell you as much as they know about it.
Regarding your friends, different public sector bodies may have different contracts and different negotiating arrangements - certain jobs may attract different pay protection.