before I added those 2 bindings, I did notice the gateway had 3 options (not 2 that you stated) they were: PayPal Direct Payment, PayPal Authorize Express Checkout and PayPal Process Express Checkout) - Im assuming you meant the *last* 2 options there. 
In my reply i said "2 options for paypal express". The first one you mention is for Direct paymant, the other 2 are for paypal express. You are using Express checkout, so the binding group for Direct Payment doesnt apply to you.
Also before I added these binding groups to my failure.php file I had noticed that there was already a binding group called "Payer Profile from PayPal Express Checkout" - wouldnt this binding group be all that I need rather then adding the 2 binding groups you mentioned - or do they contain totally different information?
they contain completely different information and relate to different parts of the checkout experience.
The way express checkout works is to pass the transaction information to paypal, the user selects the payment method and is then directed back to your site where they can select to process the transaction.
there are 2 places for the failure to occur, thus the need for the 2 binding groups
Without seeing the full request and response of a failed transaction, I really cant say what the cause of the failure is, the full response from paypal on failure is needed in order to troubleshoot, without that information I cant give any answers.
