Air passenger rights are protected by Regulation (EC) No. 261/2004, which covers the rights of passenger in instances of denied boarding, long delays and cancellations. However, under law, if a flight goes ahead and a customer cancels or simply does not use their ticket, they are not entitled to a refund. Of course, none of these legal provisions ever envisaged having to deal with the impact of something like Covid-19, and because of that there are many unfair things happening.
It is my understanding that airlines are offering re-booking and other options to passengers and passenger should contact their airline directly to discuss options.
In the meantime, be assured that matters such as you have raised will be raised with the airlines. I am conscious that as some flights come back on schedule, many more people may be affected in the same way as your constituent.