I ran -Bin4ry's Root, this takes you to the 1st step (restore), on this screen I managed to click the search (mag-glass) without the KF2 resetting (possibly this stopped the apex launcher?). This then allowed me to search for RootExplorer (previously installed) and then I could delete the Apex.apk from system/apps..... reboot all done.
However, this does make me wonder what is going on, I can install a game from google play, all good, the icon shows up (and I can search for it) run it all good. But if I try to install a launcher (apex,adw, go ex etc) they don't show up either icon or in search Any ideas why this could be? (I checked under settings/applications/installed applications/all applications/ click on apex but the launch by default button is grayed-out)
Oh, just a quick tip with the above rooting method, if your KF2 does not re-set during rooting (when it should) I just manually re-set it and all seemed to go well Also it can take a long time for the KF2 to been "seen" by the PC after re-boot, just be patient