One possible reason for the error you got during the uninstall is the existence of some [override] management pack(s) that are depending on the F5 Management Pack. The setup, by design, doesn’t remove the management packs that are depending on the F5 Management Pack, and thus cannot uninstall (and remove) the F5 Management Pack.
You can find out the management pack(s) depending on the F5 Management Pack by using the System Center Operations Console > Administration > Management Packs > select the F5 Management Pack > Properties > Dependencies > and check the list in “Management Packs that depend on this Management Pack”. You have to delete those management packs first before uninstalling the F5 Management Pack.
There could be other reasons as well for the uninstall failure. The setup.log file would tell you more about the error.
-julian