Hey man! Why do you try to make life difficult for you?
Just download the CID52 MAIN, FS and CDA, flash it to the phone with SETool2Lite, and then try to check for updates on SEUS.

The problem for you comes only if you phone was unlocked and by updating on SEUS becomes locked again.

If it was't properly unlocked, try to do it with professional tools and after that flash a CID52 GENERIC Firmware+FS+CDA, and finally you can update from SEUS whenever you want.

I have a CID52 K800i bought from Orange (branded), and after i backed-up the original Orange software i uploaded the following files:
- K800_R1KG001_MAIN_GENERIC_WI_RED52
- K800_R1KG001_FS_MEDITERR_RED52
- HB1_06_Gen_CDA102568_4_R6A_GENERIC_MEDITERR
It works fine and i can update from SEUS anytime without problems.
PS: I don't mind for the moment that the phone is not SIM Free

Be well!