Firstly, Sorry for clogging up your forum by adding a new post but I can't find the answer to my questions.
I have a SGS3 that I really like, it's my first smartphone and it's all pretty exciting.
It's running the stock ROM which is 4.0.4.
AP I9300XXALF2
CP I9300XXLF2
CSC I9300OXAALF2 (UK/Europe?)
MY QUESTION:
I'm not in any huge hurry to update but I'd like to start off with at least a Jellybean ROM
I was wondering which is the easiest/mostl likely to succeed out of the following options?:
1. Change the CSC and get Keis to update it?
2. Use ODIN and get an unbranded UK ROM or similar?
Bearing in mind I have no idea how to do either of these things, please be gentle.

If any of you live anywhere near me I could bring it round to get familiar with the process. I am pretty normal.
Cheers,
James