Question [Q] Xperia S can't boot into recovery

Hi, a long time ago I fiddled around with my xperia s, I managed to root it but I don't recall what steps I took and if I managed to do anything else. I now want to try to install a custom ROM, but all of those methods include rebooting into a 'recovery'.

I can't boot into recovery - there is no blue LED at boot and holding power up does nothing. Apart from this the phone appears to work perfectly (though a little slow). I've also tried the "Quick Boot (Reboot)" app, to no effect.

Does anybody have any suggestions?

EDIT: After fiddling around and flashing a new kernel and ROM, it seems to work ok.