Must use A2uploader from here: a2uploader and CID53? - Top Sony Forums

And use these files:

U10i_R1BA049_MAIN_GENERIC_RA_RED53
U10i_R1BA049_FS_WESTERN-EUROPE_RED53
U10i_1229-0170_R7A_Customized_United_Kingdom

OR

Try update via SEUS.