Surely this is the responsability of someone in RyanAir's Operations/Dispatch departments. In a former life as a Dispatcher it was my job to read the NOTAMS and brief the crew on anything relevant to the sector they were about to operate. An airfield/tower closure would have delayed the flight immediately the NOTAM was received.
In this case, Ops/Dispatch should have advised Scheduling so they could reschedule the flight to comply with the Dinard tower opening times thereby still maintaining their on-time performance statisics.
In an extreme case I turned up in SVO at 08:45 for my 10:45 flight back to GVA to notice it was not showing on the airport screens. On enquiry I was advised that the flight had been "rescheduled" for 20:45 that evening!! GGGrrrrr!! Eventually managed to get a reroute via ZRH and arrived home 5 hours late. SU still recorded the Geneva flight as operating on-time and this was actually caused by a tech aircraft reducing their capacity. I was consulting for them at the time so real details were relatively easy to come by.
I sympathise with Mach Buffet...30 minute reporting times are madness, as are IMHO 30 minute turn arounds. It is simply impossible for the crew to complete a full briefing and everything else that is required within that time restriction.
Bring FAA style licenced Flight Dispatchers to Europe is what I say!
Whooaahh!!!