I have unlocked all of my phones (albeit Nokias) using the following forum and never had a problem and best of all its free:
http://www.unlockme.co.uk/phpBB2/viewforum.php?f=2
Only note of warning is to read the stickies at the tops of the forums and bone up on the number of times you can input the unlock code into your Sharp before it locks you out. If this happens then a code is no good and you will need a cable solution which will cost.
Edit: It looks like your model is not able to be remotely unlocked by a code (needs a clip so you will need a cable solution often found at markets or any of about 20 dodgy electronic shops littered along Tottenham Court Rd if your in London):-
http://www.unlockme.co.uk/phpBB2/vie...highlight=gx10