With the release of ESXi 5.1 Update 1 HP also now provides a full repository release including the Utility Bundle and NMI driver: (which actually do not contain any updated VIBs)
http://vibsdepot.hp.com/hpq/apr2013/
But they still haven't updated the main metadata xml.
If you want these updates in UM automatically, you need to configure this additional Donwload Source URL:
http://vibsdepot.hp.com/hpq/apr2013/index.xml
To continue the confusing version management, the Complete Bundle is now at version "04.25.13".