Noel Clarke was bulking up during filming because his next production was going to be a cage-fighting movie. Then he landed a part in Star Trek: Into Darkness (2013) so the cage-fighting movie was dropped.
After experiencing huge difficulties in getting his previous screenplays Kidulthood (2006) and Adulthood (2008) produced, Noel Clarke set himself the test of writing a straight genre piece that would get greenlit easily. This proved to be the case with Storage 24 (2012) which was rushed through pre-production.
The original plan was to have the alien be a CGI creation. However, director Johannes Roberts wasn't keen on this approach as he had just made _Roadkill_ in Ireland with plenty of CGI and hated the experience.