Originally Posted by james_uk
my current fw says its build no. JDQ39.I9505XXUAMDM
is that correct and the same as your previous official one?
Yes I believe that was my last official firmware, both MDM and ME2 are out on unlocked devices in the UK, the majority are on MDM though.
Either should be fine, if you want to have MDM stock as a backup you can get it from the thread below, look under GT-i9505 for United Kingdom BTU (April 2013) and you will see a download link for the rom your using.
You flash them in the same way.