Plot hole: (Ep. 5) The weapon Stephen finds in a desert is a H&K G36. He states that it's not a military weapon and is mainly a mercenary weapon. The G36 is used by several police and special forces units in the world, including the British SAS, which could suggest another nation's or British government branch's involvement. Comment was probably made to deepen the intrigue of the season plot.
Whatever Happened to Sarah Jane? (1) - S1-E8
Plot hole: When Maria Jackson is running away from the alien creature, she turns left into a metal fencing. The camera shows this seconds before she runs into it, banging on it in frustration. This does not make any sense. She saw the metal fencing, so why did she continue to run into it? Why did she not turn right instead and along the park?