Coming from the same factory does not mean it is of the same quality. Specialist companies specify a standard, will often have their own staff supervising and checking production runs, they have a quality/price balance in the market place and have a reputation to maintain. ie they are sub-contracting.
Ashley's companies seem entirely about profit. They are sourcing (rather than sub-contracting).
Halfords bikes have an extremely low recall rate compared to other brands despite their huge sales in the UK. Most of the premium brands have much higher safety recall rates. There are good reason for this. Halfords goes for a general spec for average people so tend to be much stronger with higher weight limits. So they are structurally much stronger. Higher performance bikes tend to have weaker components, butted tubes, carbon fibre parts, lightweight components so they can make lighter faster bikes. However there is huge crossover of bikes and you can see a Halfords £500 bike easily competing with a £900 Specialized bike for example for very similar specs. It really depends on what you perceive as quality, some might consider safety and reliability as quality others might consider being lightweight and more performance focused as quality. Carbon fibre frames for example which are open mould tend to be stronger and safer than the frames customised for a brand. Open mould are sold all around the world with lots of different brands and made in huge numbers over many years so get perfected and improved where as propriety custom frames are obviously manufactured in much smaller quantities and could be short-lived.
You shouldn't confuse perceived quality with actual quality. We all have are own perceptions on quality or bias but there is often real data that shows which brands are reliable. Warranty Direct did a study of car reliability years ago from all their warranty contracts data and German cars were by far the least reliable but many people perceive German cars to be good quality. Where as many people believe Japanese cars to be reliable and they actually are the most reliable. Different people have different views on quality some based on the evidence and some based on their own bias or accepting marketing.
Many premium brands spend a huge amount of marketing and sponsorship where as many budget brands don't so its easy to get manipulated. Most bikes feature the same components i.e. lots of Shimano products which are the same quality whichever bike you fit them too for the same actual product. A Trek mountain bike with Tourney gearing and freewheel is inferior to a Carrera mountain bike with Altus gearing and a casette even if they do sell at the same price. There is no magic in the Trek brand being slapped on at the factory like Fuji-ta who make a huge amount of bikes for multiple brands.
Ultimately unless you have a very high budget you will always get a better bike at Halfords for the same money or less because their margin is less and logistics are so much simpler. However there are real manufacturers mixed in with basically importers, Giant and Merida are real manufacturers so the logistics gets different because they actually manufacture their own products, frames, forks, wheels etc but they still have the same range of components fitted.
Also if you are a importer basically swopping manufacturers all the time to get a better price how can quality be consistent? Many brands moved away from having their bikes manufactured by Merida or Giant because they became too expensive so went to cheaper factories so there is a quality difference between years. Cannondale has used lots of different factories and some factories have created huge issues. I remember a video by sick/supreme biker on youtube where he shows the appalling manufacturing of the Cannondale bike he bought for a customer, the assembly was completely wrong at the factory. Cannondale of the past was jokingly called 'Crack'n'fail' because so many of their frames were breaking because they made them too light and weak.
I really don't think there is any tighter controls for the premium brands at these Asian factories, I see no evidence of it at all, no data that supports it.
