I liked it a lot, and so did Pp, but I suspect it's one of those movies that depends enormously on your personal context.   It might even seem dull or confused if it wasn't a story you grew up with...

Pp correctly identified the Spitfire pilot as the designated hero of the movie, but I have to admit I was really watching for the boats, and I completely assumed that the old bloke and the two kids in the motor yacht were supposed to be the main heroes.  Where I grew up, someone had made scale models of all the Little Ships of Dunkirk and they were displayed at the local National Trust place, so that was my context.

It was a pity that I don't think they were able to show any of the Dutch coasters or Belgian ships involved, and I don't remember seeing any RNLI lifeboats either but perhaps I missed them.  It was nice to see the Medway Queen  (was that genuine? Wikipedia thinks she's still preserved... oh, hang on, maybe it wasn't the Medway Queen but the Princess Elizabeth paddle steamer?)  but I don't remember seeing any of the Isle of Man Steam Packet ferries, either, even if they had to cgi them in....  But perhaps I should re-watch now I've got over the tension of people being shot and trapped on beaches and in sinking ships (aaaaaa the sinking ferry full of people and the teacups and the floating sandwiches!  I was very tense at that point. )