Problem with Delivery_Block_HTML not showing customer's full name

[Acteon]

Hi all,

I'm having an issue with 1.7.5.0 not showing the full name when the customer has assigned gender (Mr/Mrs). It shows the FirstName but no LastName as per the image.

If the customer has not assigned (Mr/Mrs) it shows the full name, FirstName and LastName.

Which file do I need to edit to fix this?

Thanks in advance for any help.