The British Resistance

http://www.dailymail.co.uk/news/article-2066415/The-British-Resistance-The-true-story-secret-guerilla-army-shopkeepers-farmworkers-trained-defy-Nazis-suicidal-stand.html

An excellent article about a once-obscure subject that's only being explored seriously now.  The movie sounds pretty neat, although I take strong issue with the implication that in 1944 Germany was going to be launching an invasion of Britain, (regardless of the success or failure of the D-Day invasion).  But in the Summer and Fall of 1940 this was a VERY real threat, narrowly averted, primarily by the success of the British during the Battle of Britain air war and the unpreparedness of the Germans for such operations in the short-term.  But it was damn close.
A German invasion has been one of those 'what-if' scenarios debated by historians since the War. My understanding is that the consensus leans towards a German success. I tend to disagree. I believe it would have failed, but at the sacrifice of both the Royal Navy and Air Force. What might have happened under such circumstances in 1941 then becomes the next big what-if...
As for the Resistance during an occupation, I go with the current view - these guys had a half life of about two weeks.  The brutality in the reaction would have been monstrous.