S2 simlocked=carrier locked?

Hi,
 i would like to ask, what is the difference between sim locked and carrier locked?
If the phone is sim unlocked but carrier locked, is it means that, it can only use the 'locked' network??

and, any recommendation on where to unlocked it at sheffield area?? around city centre?

simlock has two meanings.. some times people mean it as network lock while some other time the sim itself gets locked. in latter case you need PUK code to make it unlocked. in your case your phone was initially sim locked and got it unlocked using PUK code and now it is carrier locked. And to answer to your second question, yes your phone will only work with the locked network . to get it unlocked from your carrier you need unlock codes. you can get the unlock codes either from your service provider or from other online providers like Prounlocking.com