I doubt you can do it yourself because when I had my phone unlocked they plugged it into the computer to do it....... ASDA themselves wont do it, you will have to either call the mobile phone operator who can possibly do it for you for free or take it to a mobile phone shop which I did an it cost about £5 so it wont break the bank
This supports the 2300 however it should do the 2310.
And those dodgy mobile shops, all they do is use this or some hardware ( for bb5 phones, similar to http://www.fonefunshop.co.uk/Unlocking/bb5box.htm ) that enables them to delete all the software and firmware and reinstall it without the operator crap.