The Halfords mega store thing in Plymouth is no good either in terms of tech skills
My bro and I were out cycling and were nearby so popped in so he could pickup a bottle cage and a set of lights for his new (brand new) bike. He wanted to fit them there and then so the lads behind the counter were very accommodating but we found the lower down tube rivnut was turning when we tried to tighten the bolt
So we asked if we could borrow their rivnut gun, not only did they not have one, they'd never heard of them, nor did they think the problem was fixable, they thought the frame was beyond repair(!)
But to their credit they were cool with lending us tools
The bike came from Evan's in Bristol, naturally they are fixing it free next weekend, we'd fix it ourselves but the little bolt won't fully undo
So I guess with Halfords the advice would be: Set your expectations accordingly, like PC World, Comet or whatever, I doubt the guys in there are very well trained or paid