Jailbreak UK but not Unlock

[Claret73]

Hi

Different query here to the Jailbreak/unlock methods...

If I was to buy a UK Phone & activate it with an O2 Contract (which I'd like to do as with the unlimited Data & Cloud WIFI it kinda knocks a fair bit off the bill in theory), could I then Jailbreak it so that I could install & use 3rd party apps?

Would this affect my legitimate activation?

If this was OK to do, are there any things I'd need to consider so's that once connected to ITunes I'm not gonna brick it...
Cheers
Andy

[RickyGervais]

You can do that, but you should be warned that it will invalidate your iphone warranty

[Claret73]

You can do that, but you should be warned that it will invalidate your iphone warranty

Does it seem I'm doing something unnecessary??...Is it worthwhile Jailbreaking? What are benefits?

[RickyGervais]

access to third party apps