a) your personal experience - and putting a date to it would be interesting
your perception based on other people's experience
c) whether your opinion of Halfords has in any way been shifted by the racing team
a. I've bought two childrens bikes from Halfords, before I got back into cycling properly. One was a very small bike with stabilisers. I went through the "sales checklist" (PDI) that they had ticked off and they'd obviously just ticked through it without checking anything on the list, as the tyres were completely flat and one of the points was "Check correct tyre pressure". That was about 4 years ago now.
At around the same time I bought a larger bike for my older child. This is a BSO, but I didn't know any better at the time. It's very heavy and was poorly set up when I picked it up. It didn't change gear correctly and the chainset was bent, damaged in transit. It's only because of the experience I had buying the first bike that I checked through everything before accepting it. They fixed it.
A positive experience. I needed a new 7 speed freewheel for my bike (again, approx. 4 years ago) and they sold me a new one and changed it one the wheel free of charge. The staff in the maintenance section were very helpfull.
I tried to buy a helmet and some other bits and bobs from them (again about 4 years ago) and the helmet was 30% off. When I got to the till they charged me the undiscounted price. I refused to pay it, and when I took the cashier to the shelf I'd got the helmet from, the signs showing the discount had been removed. I spoke to the manager and he refused to tell me if they'd had a promotion on those items recently, and refused to sell me the helmet for the price it had been advertised at when I picked it up off the shelf. I left without the goods, and I've not made any purchase > £10 from them since.
b. I was cycling home from work about 3 years ago and came across another cyclist walking along the side of the road pushing a bike and covered in blood. He'd been riding his new bike home from Halfords when the steering had come loose. Unable to control the bike because the handlebars were rotating around the fork he'd been thrown off the bike into the road in front of a bus. Fortunately the bus had managed to stop without running him over but he'd got quite a cut up face and hands.
30 seconds with my multi-tool and the steering was done up tight enough to get him home.
c. No.
My perception is that they have some good mechanics, but an awful lot of rubbish ones. They'll rip you off if they can get away with it, and they sell an awful lot of heavy tat with wheels, and the occasional decent bike.
I avoid unless I'm desparate for a part they I know they'll have, as they are the nearest seller of bits to my house. If I had a closer bike shop I would use them, and I frequently go past two Halfords on my way to a proper bike shop when I'm able to plan out getting parts rather than needing something in an emergency.
I advise everybody I know to use a proper bike shop instead for any major purchase.
[EDIT] : Whoops. Missed d. I'd suggest that they get some properly trained staff, and give them enough time to do a proper job. If the mechanics were good I would consider using them. As it is I avoid.