Hi Matthew,
Not quite sure I understand your scenario....
Also, the labelling of the template override has changed slightly between Zenoss 3.x and 4.x - which are you on?
Basically, as you suggest, the "Override Template Here" action (In Zenoss 4) creates a local copy of the device template, which you can then modify to suit a specific machine. Once you have done that, if you go to ADVANCED -> Monitoring Templates and look for the name of the template, you should find that there are 2 entries - your initial one applied to the device class and the specific one for the device. You can modify any template from this menu if you wish to.
The other use for the "Copy / Override Template" action, from this Monitoring Templates menu, is to copy a template applied to one class, to another class. Again you will get a whole new template that you can modify.
If you have a local template copy applied and want to revert to using the class template, from the device's page use the Action icon and "Remove Local Template" - it will prompt for which template you want to remove. It should then revert to using and defined inherited template. If you want to restore a local template then you will need to recreate it again.
The other alternative if you have a local device template that isn't working and you want to disable it entirely, would be to disable the data source. For the HttpMonitor one this is very simple as there is just the single HttpMonitor data source. Double click and edit the definition to untick the "Enabled" box. You then have NO effective http monitoring. It won't revert to the class template unless you completely delete the local device template.
Cheers,
Jane