Adding Ajax to Webforms in Drupal 7 - Ajax Submit

I'm using Webforms 3.x and Drupal 7.x.

I'd like to be able to use Drupal 7's Ajax features to provide a confirmation message via Ajax on submit.

To achieve this, I'm hoping to modify my form using a HOOK_form_alter.

The $form array provides the submit element at $form['actions']['submit']. If I add an ['#ajax'] attribute here, the action takes effect when submit is actioned by the use, and the callback function specified is called.

It seems that webform initiates two callbacks from

$form['#submit'][0] = webform_client_form_pages

$form['#submit'][1] = webform_client_form_submit 

My question is, how can I initiate the necessary webform callbacks on Ajax submit? I'm not totally familiar with webform, or how it deviates from standard FAPI (or if it does at all).

Any advice appreciated.