Add text shipping value in Opencart - php

Question

We provide emailed quotes after an order is recieved in OpenCart. How can I add a field to show TBC instead of £0.00 in OpenCart. We use X-Shipping for our 4 delivery options:
Is this possible?
Here is the PHP code for the catalog side
<?php
class ModelShippingXshipping extends Model {
function getQuote($address) {
$this->load->language('shipping/xshipping');
$method_data = array();
$quote_data = array();
for($i=1;$i<=12;$i++)
{
$query = $this->db->query("SELECT * FROM " . DB_PREFIX . "zone_to_geo_zone WHERE geo_zone_id = '" . (int)$this->config->get('xshipping_geo_zone_id'.$i) . "' AND country_id = '" . (int)$address['country_id'] . "' AND (zone_id = '" . (int)$address['zone_id'] . "' OR zone_id = '0')");
if (!$this->config->get('xshipping_geo_zone_id'.$i)) {
$status = true;
} elseif ($query->num_rows) {
$status = true;
} else {
$status = false;
}
if (!$this->config->get('xshipping_status'.$i)) {
$status = false;
}
if (!$this->config->get('xshipping_name'.$i)) {
$status = false;
}
$shipping_cost=$this->config->get('xshipping_cost'.$i);
$free_shipping_cost=(float)$this->config->get('xshipping_free'.$i);
if(empty($free_shipping_cost))$free_shipping_cost=0;
if ($this->cart->getSubTotal() >= $free_shipping_cost && $free_shipping_cost!=0) {
$shipping_cost = 0;
}
if ($status) {
$quote_data['xshipping'.$i] = array(
'code' => 'xshipping'.'.xshipping'.$i,
'title' => $this->config->get('xshipping_name'.$i),
'cost' => $shipping_cost,
'tax_class_id' => $this->config->get('xshipping_tax_class_id'.$i),
'text' => $this->currency->format($this->tax->calculate($shipping_cost, $this->config->get('xshipping_tax_class_id'.$i), $this->config->get('config_tax')))
);
}
}
if(!$quote_data) return array();
$method_data = array(
'code' => 'xshipping',
'title' => $this->language->get('text_title'),
'quote' => $quote_data,
'sort_order' => $this->config->get('xshipping_sort_order'),
'error' => ''
);
return $method_data;
}
}
?>