Agreed on both Home Guard and Mayan; it would have added much emotional depth and more of a dilemma to our heroes if things had been more shade of grey. As mentioned in my own comment, I think the Malcolm character instead of an unconvincing ex should have been an old comrade from the war whose trauma had driven him to xenophobia and then to violence; someone tragic, rather than an obvious slime bag the audience could only despise. And I like your idea about Mayan.