My son-in-law has a Carrera Subway, and is very happy with it. As delivered by
Halfords, gear change was poor, but, I adjusted it correctly, and, all is fine. SiL says it is much preferable to his previous (Giant) mountain bike (I did advise him it would be, for the type of riding he does).
My youngest daughter also has a Carrera Subway, which she totally neglects, but, uses daily. It worked fine straight out the box, once assembled, (click and collect).
On balance, I would say the Carrera models are fine, Halfords service is a bit hit and miss, in my experience, but, that would be true no matter the brand.