i9300 3UK with CM9.1, NELF1, callers here garbled voice.

I have an SGS3 i9300 on Three UK.

I flashed it with CM9 then updated to CM9.1

I am on I9300NELF1 baseband.

When I make calls the person I'm calling says that they can't hear me properly or that it sounds like my signal is poor. When they say this I cycle speaker-phone on then off again and the problem is gone.

I wonder if I need to update my baseband to a newer version (one that is fully compatible with Three UK), however I can't seam to find the information on how to do this, or if I can do it without a full reflash?

Thanks for any help you can give in advance.