From my own experience of this shambles, last week I was on one of the training courses run by G4S. Of the 220 expected, 30 turned up. On given instruction to write an alphanumeric code on a form, one of the letters was given as E Echo, which one of the candidates promptly wrote as A. There seemed to be quite a few people with foreign passports and Visa's who struggled a lot with English. As far as security goes, most of them would be as useful as a chocolate tea pot.
As for G4S, I still haven't received role specific training, security passes, uniform, deployment instructions, or even told what role I'll be playing.