Dear Dave
Perhaps there was something wrong with your update 2 download. It worked OK for me. If you really want to you could try downloading update2 again.
Anyway, my understanding is that each newer update totally supercedes and includes/relaces the earlier update. Based on this you only need apply update3 to a standard v5.5 instal, ie everything (or better) in upd1 is in upd2, everything in upd2 is in upd3.
rpm -qa
will show a list of all packages installed, browse thru it to look for the updated packages.
Regards
Ray Mitchell