Jailbroken IPAD 1 3G Locked to Carrier

[mrparm]

1st of all Thank you to those who have taken the time to read my post and make suggestions.

1 - The version on the Ipad is 4.2.1 - should this be updated and will I lose the jailbreak ?
2 - The Ipad was not locked when I recieved it however is now locked to 3 since I put a 3 PAYG sim in it, how do I unlock it ? the only solution that I can find refers to restoring the Ipad which I do not wish to do.

Thanks