It always was a non-refundable booking. The problem was that when I made the booking with my original check out date Hotels.com did not reveal to me that I could not leave the hotel because of the religious festival which prohibits travel on my check out date. Only once I made the booking and paid did they tell me on the confirmation that travel was prohibitive.
As the booking was made in UK I need to ascertain how I pursue a refund as the booking was accepted without the travel ban being revealed at the time of booking. I believe that this contravenes UK trading law.