imo (notice that! lol) you'd be better buying a cheap "brand name" bike than an expensive halfords bike..... The quality and general build quality would be far better, and represent better for value for money in the long run. Also you're paying for quality parts, not some ****ty knock off copies made the cheapest way possible!
unless you spend decent money on disk brakes you're going to get tat. you'd honestly be better off buying some decent v brakes as if they're set up properly are far better than some rubbish quality disk brakes! (and probably still cheaper!)
I sort of agree with you there Zmaricz, certain expensive halfords bikes are actually not very good at all and simply have the price bumped up so it can be advertised as reduced later. However when apollo bikes are cheap, about £70 for the XC26 and about £120-£130 for the XC26s then they're reliable enough to be worth the money. I wouldn't recommend any of the FS Apollo bikes, the rear suspension is too cheap and hinders performance. I also don't reccomend the XC26SE, it's too expensive for the specs.
Also Carrera bikes, which are halfords more expensive bikes, are actually very good value for money if you can get them cheap. The cheapest Carrera bike, the Vulcan, is normally £300 with disks and £250 with v brakes. However these generally go into clearance in january and can be picked up for sometimes £100 less.