Thanks for your response and apologies for the delay in getting back to you.
I can confirm that my page is in fact a page, I've also tried both snippets you have provided without any success.
Only one page is displayed on the URL, you can see here for an example page: http://www.livefreedietravelling.com/terms-and-conditions/
I'm using a theme called Sahifa, and as the theme developer states, there is no custom processing on featured images (http://themeforest.net/item/sahifa-responsive-wordpress-newsmagazineblog/discussion/2819356?page=153).
If you are happy to provide an email address, I can email you the corresponding pages of the theme (if you are otherwise unable to get hold of it) for you to check over the code?
Thanks again for all your help, it's greatly appreciated.