If you know the fundamentals of the controversy - Wodehouse's naively well-meant wartime radio broadcasts while in German captivity and the fury they aroused among some in Britain, so staining his reputation that he never returned there - this film will tell you nothing new, and will merely confirm your assumptions: "Plum" childlike, unworldly, escaping into his fiction; wife Ethel feisty, sexy, cannier; Malcolm Muggeridge stalwart and decent; stepdaughter Leonora loyal and devoted; conniving Nazis, etc. They are all just cardboard.
A critic described the cast of the recent Godzilla/Kong movie as not so much characters as "Exposition Delivery Units," and that wonderful phrase - or sometimes its corollary, Message Delivery Units - occurred to me when a British official (supposedly Alfred Duff Cooper, but it could have been anyone) launched into an angry speech to a subordinate, something on the order of "Don't you understand, Wodehouse's broadcasts to the Americans are undermining the war effort, we British are in grave trouble, our shipping is down XX percent to the Nazis and if we don't bring the Americans in, we'll lose the bloody war," etc. At another point, Wodehouse's stepdaughter - who has only a dozen or so lines in the entire movie, every one of them strictly functional and by-the-numbers - actually declares, out of the blue, "I wish I wasn't going into a hospital," and her fond husband - who has even fewer lines - actually replies, "Darling, it isn't a serious operation." (Of course she dies. How could she not? And incidentally, when Plum and her mother learn of her death, their shock and grief are so tepid and unconvincing that the scene is downright embarrassing.)
More exposition: Wodehouse is described - and I assume this is speaking for the screenwriter - as "a kind of saint," and toward the end, in case we needed things to be made even clearer, Muggeridge intones, "He isn't equipped for this nasty little century...its lies and cruelties and distortions." (To show his anger at one point, Muggeridge proceeds to overturn a table in a Paris hotel restaurant.) We also have a scene where the stepdaughter speaks long-distance to Wodehouse's American agent while, in a convenient comic-book touch, a Blitz bombing is actually going on. In a later scene, this stepdaughter, hearing Wodehouse attacked on the BBC, begins answering back to the radio, drowning it out before she's even heard more than a few sentences - and then she angrily switches it off! That's not how someone behaves when they hear something shocking and unexpected over the radio; they listen, appalled, to every word.
The movie is very pretty to look at, with beautiful period decor, but its small cast and limited story line made me think that it might actually have worked better as a simple stage play, with a few bridge chairs on a bare stage, where the dialogue might not have seemed quite so contrived and artificial. But even then, we still wouldn't leave knowing anything more, or understanding anything more, than we did when we came in.