Many thanks. Our website is managed by a their party. Unfortunately I do not have access to functions.php to add the code, but that is not a problem we can ask the third party to do that for us. I just wondered if I could add it to the script section of the form, but I did not notice it was PHP and not java script.
I think I will asked our service provider to add the code for us, rather than installing another plugin, just to keep the number of plugins as low as possible.
Once again thanks for your quick reply, and brilliant product.