Quick one! Ebay iPhone-checking carrier & unlocking

[lordra]

Hey guys,
There is a phone being sold on eBay for spares or repairs, that is in perfect working condition except that it's blocked. Now, it's blocked only in the UK & will work outside of our Borders.
What I want to know is, if the iPhone was previously LOCKED to a network, say, O2, and it was taken to France, would the locking restrictions still apply?
Is there any way to check what carrier it's locked to?
Is there any way to check if it will work abroad on a holiday rather than actually taking it there?

[lordra]

Update+bump:
If the phone is locked and then restored, would it ask for the original sim or just any sim?
Alternatively, if it is UNLOCKED and then restored, can I use any sim in it to activate?

Will this mean that it's unlocked to be used with anything?

[sfkassem]

If the iPhone is locked to a specific carrier, then you must use that carrier's sim to activate it (unless you are going to hacktivate it).
If the phone is Unlocked then you can use any sim card to activate the phone as the activation takes place on apples server which responds to any sim if your phone is unlocked