where the form field LEDProductUpdateDate already uses the Y-m-d format that the database requires, you do not need to use any additional formatting funcitons
<?php echo date("Y-m-d H:i:s"); ?>
formatting functions would only be \needed if the form element used a different format.
the function would need to be defined before the update record code, the used in the update record code like this:
$WA_fieldValuesStr = "".((isset($_POST["LEDstock"]))?$_POST["LEDstock"]:"") ."" . $WA_AB_Split . "".((isset($_POST["LEDProductUpdateDate"]))?formatUKDateMySQL($_POST["LEDProductUpdateDate"]):"") ."";