1) Official - Handing in the Xperia at Sony Service center You can request to have 2.3 installed on your phone ( warranty would remain )
2) Unofficial- Flash Gingerbread using Flashtool (your warranty would get void)
Here is how
Remember flashing may void your warranty and you are doing it at your own risk.
This is how to downgrade
1)-Download flashtool- Flashtool and install it
Go to C:/ Drive > flashtool > firmwares > delete everything present and exit
2) Use saved rom from step 2) above or download rom
Live with walkman ROMs :
3) NOTE: only .ftf files to be placed
Place .ftf file as follow- copy .ftf file to C:/ > flashtool> firmwares > and paste
4) Run flashtool> click on the flashing icon ( left side below "file" option),,,Select flashmode > ok
5) left side you must see your firmware name and contents, if you are not able to see contents then use an older version of flashtool ,, on the right side mark boxes as
select ok
6)Wait for it to prepare and it will ask you to connect your mobile, follow the steps carefully and connect flashing will begin and flash
Done 
