in all seriousness (I confess, Bandini, that I am the bike fascist, and the noble McB the broadshouldered recipient of what passes for advice) any LBS is going to charge you a lot more for sorting out a
Halfords bike than the margin between the Halfords price and the price they'd charge for a comparable, or better, steed. My brother, who owns an LBS, regularly sees bicycles bought mail order or from Halfords that need work that is both neccessary and futile - futile because the quality of the components is irredeemably crap.
So when you buy a bike at Halfords, or mail order, and you want to avoid it being one of the hundreds of thousands that are consigned to history every year you sort of accept that this is a bit of a project.