That story is quite shocking, especially the thought of someone riding away on a bike with loose handlebars.
I'm not trying to defend
Halfords culpability in any way, but I have bought 3x bikes from them during the last few years, and all have been set-up ok. I had to do some minor fettling as you'd expect, but nothing that compromised their safety (this is the Foss Islands Road branch, York).
The question in my mind (and I don't know the answer to it) is where the hell in their process is their quality control at the point that a bike is handed over to a customer? Is it non-existent?
Presumably on my 3 bikes I must have had reasonably competent "mechanics" putting them together, so the "quality control" element would presumably be built in to their level of personal competence (as would be the case for any independent bike shop). But if the "mechanic" is inexperienced, and that is known to be the case, then how can they possibly think it is ok to hand a bike over to a customer without someone competent checking it first?