Java doesn't clean up after itself when doing a program update. I handle that issue by un-installing the old Java installation before install a new version. That way only the latest Java extension and plugin is in Firefox, the older ones were un-installed.

Thanks. Should have worked it out for myself but wasn't sure whether deleting the list of Java Consoles would disable it altogether and cripple FireFox

I have noticed this. One reason for software changes is often to fix security problems. I would guess with Java Console they leave older versions available for the sake of backwards compatability with older applets.

I understand that only the latest JRE needs to be kept, if compatability issues arise I believe any other versions are downloaded as required.

see also http://en.wikipedia.org/wiki/Java_applet

and for long details about Java Consoles, in various versions of Firefox, including mention of uninstalling problems look at http://kb.mozillazine.org/Java#Multiple_Java_Console_extensions

Of course any discussion of Java Consoles probably needs the reminder that JavaScript and Java are not the same thing.

JavaScript does not need the Java Console or any Java Runtime Environment. see

You can uninstall (remove) the Java Console extensions and disable the Java Quick Starter extension, you do not need them to run Java applets.

See http://kb.mozillazine.org/Java#Multiple_Java_Console_extensions

Disable the Java Quick Starter extension: Tools -> Add-ons -> Extensions

• Control Panel -> Java -> Advanced tab -> Miscellaneous -> Java Quick Starter (disable)

See http://www.java.com/en/download/help/quickstarter.xml - What is Java Quick Starter (JQS)? What is the benefit of running JQS? - 6.0