Thank you Jason.
And would the URL convert from this:
https://www.facebook.com/tr?ev=6018866625924&cd[value]=0.00&cd[currency]=GBP&noscript=1
...to this?:
https://www.facebook.com/tr?ev=6018866625924&cd[value]=<?php echo $cartName->GrandTotal(); ?>&cd[currency]=GBP&noscript=1
Thank you.
NJ