Ok, I've tracked it down to a widget in the default 'Magic' skins parameter file.
FTP into your box and download:
/usr/share/enigma2/Magic/skin.xml
Open this file on your PC in a text editor and find the widget parameters starting at line #114:
<widget backgroundColor="black" font="Enigma;16" noWrap="1" position="54,214" render="Label" size="300,22" source="session.CurrentService" transparent="1" halign="left" valign="top" zPosition="3">
<convert type="CryptoInfo">VerboseInfo</convert>
</widget>
Encapsulate this in comment tags:
<!--<widget backgroundColor="black" font="Enigma;16" noWrap="1" position="54,214" render="Label" size="300,22" source="session.CurrentService" transparent="1" halign="left" valign="top" zPosition="3">
<convert type="CryptoInfo">VerboseInfo</convert>
</widget>-->
Save the file, FTP it back up to the box and then reboot for changes to take effect - FTA or Server/ECM times should no longer be displayed