Android 4.1.2 official Jelly Bean LT22i Xperia PDownload Firmware: Here
Jelly Bean Android 4.2.1 Official (ie you got the firmware without modification or weird stuff, original).
Do not wait until your carrier will deign to send the update.
No update because you lose is updated in 5 minutes
All customization of your Xperia and garbage that puts your carrier, as their logos and Apps and stuff appalling.