Took this one stage further:
(a) Created an order status called 'unpaid'.
(b) Added the following code to listing.php.
echo '<span class="hikashop_order_listing_status">';
	echo $this->order_statuses->trans(ucwords($row->order_status));
  if ($row->order_status == 'unpaid' && empty($row->show_payment_button)) {
    $row->show_payment_button = true;
		$pluginsPayment = hikashop::get('type.plugins');
		$pluginsPayment->type='payment';
		$this->assignRef('payment',$pluginsPayment);
		$config =& hikashop::config();
		$payment_change = $config->get('allow_payment_change',1);
		$this->assignRef('payment_change',$payment_change);
  }
echo '</span>';
(c) This gives the store owner the ability to change the payment method / order status and then customer is able to pay using the 
Pay Now button. E.G. If they chose pay on delivery, but then decided / were asked to pay in advance by Paypal - or there were other issues with the order which required negotiation.
(d) An interesting feature I spotted when adding the order status is that Hikashop supports a heirarchy of order statii. I.E. I created 
unpaid under 
created - are there plans to use this feature in the future - maybe possibilities of enhancing what I have just done even further.