I had a reply from paypal.
They suggest the problem lies with using the older API script 63.0 and that I should use the newer one instead
"Through the investigation that has been made on the issue raised by you, I am afraid it is not the problem with notification email but something on the older API version used which is 63.0.
This might be the reason why the item description can't be passed to us successfully. I would suggest you to change newer API version which is 115.0 and try again."
I would have thought that if this was truly the case, then everyone using this script would be affected ?
I'm kind of stuck now, in that my code doesn't generate an accurate email receipt, (though the transaction is successful)