Use these files:

1. W890_R1EA033_MAIN_GENERIC_AK_RED52
2. W890_R1EA033_FS_FRANCE_RED52
3. W890i_1204-5401_R2A_Customized_FR_France

Then update with SEUS to last version R1FA035.

"Problem is that now the phone drains battery MUCH faster than before the upgrade." - just stop 3G from here:

Menu > Settings > Connectivity > Mobile networks > GSM/3G networks > Only GSM