My Samsung Galaxy 3 mini shows 'Emergency calls only'?

I managed to forget my passcode on my S3 mini but as the 3 button recovery (power + vol up + home) didn't work I had to use odin to put a restore ROM on it so I could wipe the phone back to factory settings.

This worked and the phone is now back on and accessible but for some reason it now only shows 'Emergency Calls Only'. The phone is locked to O2 (UK) and I have tried 3 different SIM cards in it and they all show the same thing, even though it seems to have signal and O2 shows in the carrier list if I perform a search.

I'd looked around for a fix for this and there were mentions of it being something to do with the modem/baseband, I'm still new to android and rooting so any help you give please give as if you were explaining it to an idiot.

The phone is out of warranty so I cant take it back and I cant really afford to take it to a specialist. So any help will be hugely appreciated.

Thanks

Read more: My Samsung Galaxy 3 mini shows 'Emergency calls only'?