//change BACS fields
//original fields from plugins/woocommerce/includes/gateways/bacs/class-wc-gateway-bacs.php
add_filter('woocommerce_bacs_account_fields','custom_bacs_fields');
function custom_bacs_fields() {
 global $wpdb;

 //Added by Red Lorry.
 //Get the first item in the cart.
 foreach( WC()->cart->get_cart() as $cart_item ) {
    $product_id = $cart_item['product_id'];
    //Get the product vendor based on the $product_id.
    $vendor = get_wcmp_product_vendors($product_id);
    //Get the form_id of the vendor.
    $vendor_form_id = (int)get_user_meta($vendor->id, 'wcmp_vendor_registration_form_id', true);
    //Get the vendors form meta data.
    $vendor_form_data = get_post_meta($vendor_form_id, 'wcmp_vendor_fields', true);
 }
 //Get the product vendor based on the $product_id.
 $vendor = get_wcmp_product_vendors($product_id);
 //Get the form_id of the vendor.
 $vendor_form_id = (int)get_user_meta($vendor->id, 'wcmp_vendor_registration_form_id', true);
 //Get the vendors form meta data.
 $vendor_form_data = get_post_meta($vendor_form_id, 'wcmp_vendor_fields', true);
 if ( !empty($vendor_form_data) ) {
  $account_details =
   array(
    'account_name'   => $vendor_form_data[4][value],
    'account_number' => $vendor_form_data[5][value],
    'sort_code'      => $vendor_form_data[6][value],
    'bank_name'      => $vendor_form_data[7][value],
    'iban'           => $vendor_form_data[8][value],
    'bic'            => $vendor_form_data[9][value]
  );
  $account_fields = array(
   'bank_name'      => array(
    'label' => 'Bank',
    'value' => $account_details[0]['bank_name']
   ),
   'account_name'   => array(
    'label' => 'Account Name',
    'value' => $account_details[0]['account_name']
   ),
   'account_number' => array(
    'label' => __( 'Account Number', 'woocommerce' ),
    'value' => $account_details[0]['sort_code'].' '.$account_details[0]['account_number']
   ),
   'bic'            => array(
    'label' => __( 'BIC', 'woocommerce' ),
    'value' => $account_details[0]['bic']
   )
  );
  return $account_fields;
 }
}