There is quite a difference: authorisation is permission granted by someone else- I was authorised access to the building by security. Authorisation is usually used when something is exclusive, and in order for you to be allowed to do something- someone else who has that authority grants it to you.
Entitlement on the other hand is something you have intrinsically: essentially it is a right you have that no one can take away from you. e.g. I am entitled to borrow 5 books from the library as part of my membership; I was entitled to voice my opinions to my teacher, regardless of her opinion.
Hope that helped