Their life expectancy would have been no more than a few weeks. Their Group leaders and Intelligence Officers were regular Army.
The German invasion thankfully never happened but methods learnt were then used by the S.O.E. and members of the Auxiliary Units went on to fight in Europe, including alongside the Résistance in Operation Bulbasket in the South West of France. (link)
British Resistance archive (link)
Auxunit news - website dedicated to the Auxiliary Units (link)