Otel.com - Not Refunding Booking for Closed Hotel

I think it’s pretty clear-cut that a non-refundable hotel room charge becomes refundable if it transpires that the hotel is closed for the relevant dates.

I think so too. My worry is trying to get an answer from an operator who may go under. Hopefully the Card Chargeback will work though.
 

My experience was excellent with Booking.com too. I had a number of bookings in the USA for this year and they have arranged refunds back to me despite the bookings being 'non refundable'.

I think it’s pretty clear-cut that a non-refundable hotel room charge becomes refundable if it transpires that the hotel is closed for the relevant dates.

Agreed - unless you are happy with a voucher, it's a clear cut case that if they can't provide the service the non-refundable issue goes away.