[eluser]xwero[/eluser]
the data is in the _field_data[$field]['label'] Form validation class variable. You can extend the class with a label method and add a label method to the form helper that takes care of the html generation.
But if you store all your labels in language files you can use the language helper to generate the html. With this approach you don't need to extend the framework and you don't have to change code if more languages are needed.