If you want to debrand your phone, which I think you do. Then you will want generic firmware and custom files.

If you live in Europe then you might want to try these files:
MAIN: K800_R1KG001_MAIN_GENERIC_WI_RED52
FS: K800_R1KG001_FS_EUROPE_1_RED52
Custom: HB1-06_Gen_CDA102568_10_R6A_GENERIC_EUROPE_1

MAIN & FS need to match in the CID (52) and the version (R1KG001).
FS & custom need to match in the region (EUROPE_1)

you can download these files from this site. But you need to be a premium member, so pay 2 Euros or wait a month and post 20 useful posts on here. Or you could try other websites such as iProTebe.cz - Sony Ericsson - download
or
SE-NSE Forums (Powered by Invision Power Board)

good luck.