This is the new official 9780 OS 188.8.131.523 (Bundle 2830, Platform 184.108.40.206) released recently via T-Mobile UK
It's the full official OS, but just a home made installer thanks to Lyricidal as it hasn't been released on the T-Mobile website yet (only via the BlackBerry Desktop Manager)
1) Backup your device using the BlackBerry Desktop Manager first. (Mandatory step incase the Loader fails to restore your backup)
2) Install OS 220.127.116.110 first
3) Install OS 18.104.22.1683 over
4) The installer will show you a preset path to install the files, DO NOT just click NEXT, make sure to click on the little dotted icon to Browse, then manually navigate to the OS path on your computer which is usually located in:
C:\Program Files (x86)\Common Files\Research In Motion\Shared\Loader Files\9780M_v22.214.171.1240_P126.96.36.199
The OS folder name MIGHT be different for you if you installed the Multi Language Version or the All Lang version, thus, ensure you do this step carefully to overwrite the proper folder. If you need help with this, feel free to ask.
5) For best results, do 2-3 battery pulls and allow 24-48 hour "settling" time.
Credit goes to: Lyridical for the compilation of the installer!