Okay, thanks for the info. Sucks that hot booting is not available but the method you posted seems fair enough.
I still have one question slightly related to this. In my previous phones the recovery has been installed separately (separate ramdisk and maybe even kernel?). Have I understood correctly that in Xperias the recovery is included in the boot.img instead of recovery.img and it depends on bootloader sent parameters whether the phone boots recovery or the normal mode? In other words if I install sometimes in the future a custom ROM and the recovery included is somehow broken I have to fix it via fastboot?