This post is probably already late for party, but I wanted to share with you a website I've done in june 2013 first for checking the availability of new firmwares for the Sony Xperia Z phone and then expanded to more Sony devices.
Sony firmware check
This is a website (which works very nicely from mobile, too) to quickly check if Sony has released a new firmware for your phone model based on your Customization ID number stored inside your phone.
It allows you to save a bookmark for your very own phone (I have one myself on my phone homescreen) and it also allows you to have a dynamic image to insert in your signature on forum boards for brag and stuff.
It does NOT (yet) allow you to download FTF firmwares from different regions. If you need an update check AND a sort of FTF files index, I suggest the awesome updatechecker (for Windows) by Macmol.
This is the website: http://scavenger.ch/xperiaupdate/
I hope you can find it useful. Any (good or bad) feedback is very welcome.