I must admit that I'm a bit of a sucker for old black and white British war films and this is one of my favourites. Of course, not all are good and judged against today's standards probably few are great. But even without making those comparisons this is a pretty good effort at portraying life on an English airfield during the Battle of Britain and it balances an element of good humour with the seriousness and tragedy of wartime.
The characters are well defined by some solid performances (especially from Jack Hawkins as you'd expect in a role like this), and they go about their business with a typically stiff upper lip. What gives the film its strength though is the treatment: most of the action takes place off screen and our connection with it is largely through radio communication between the ops room and the pilots. This adds to the tension and keeps the audience involved in the claustrophobia of the ops room and the relationships which take place within it. Unfortunately the film does occasionally waver from this by showing the odd cutaways such as vapour trails in the sky (without an aircraft in sight), shots of the approaching bombers (probably the worst special effect you'll ever see) and the farmer with his cart which seems to have been dropped in as an afterthought.
Certainly one to add to your collection of you like this kind of thing.