Hi Simon,
A big fan can be a blessing if one can use shore power. We were in Siracusa, Italy for a month one Aug. and stayed at the marina (G was recovering from an injury) and it was the hottest in decades: 35-40C (90-100F) every day. We bought a big window fan and installed it to pull air from one end of the boat to the other basically 24/7 for the whole month: made a huge difference. Used the smaller internal DC fans for “aimed” air movement. We were certainly hot, but not unhappy. And we did not have that closed in feeling. Gave the fan away when we left.
My best, Dick