Terrible soundmixing
Just watched this for the second time, with headphones on (so not to wake up the neighbours) - the sound mixing in this is all over the place. I didn't notice it on speakers, but the volume levels of people's speech goes up and down in certain sequences - this could also be to do with bad boom work. I don't know an awful lot about this technical side, but it was extremely noticeable.
By the way, I thought this was a brilliant idea, but patchy. Some great moments - but Reeves and Mortimer doing really bad camp? And Ron Culshaw totally wasted as Blair? And the Chaplain joke wasn't great either (watch Charlie's own "The Great Dictator", which *really* uses this joke and runs with it)
The bits I did enjoy were Hitler on the bus, the palace radio announcer and storm troopers in palace uniform - and the ending on the cliffs... Strangely enough, in real history a lot of English aristocrats, including parts of the royal family, were quite Naziphile before the war - see the Anglo-German fellowship etc