Take it to your shop with a receipt. They are obligated to check it over and make sure it's fit to ride if they build it. Though I'm not sure if that's the case with a self built bike.
Hi there, im not worried about the gears or steering, i can sort that out, its the front caliper thats annoying me it just dosent work, its not safe
It's not just the gearing and steering. They are obligated too supply an item that is fit for purpose.. Slippy gears, bad steering and brakes that work when they decide too aren't meeting those standards and should be rectified by the supplier free of charge.. I know any GOOD bike shop will set up a bike and give you a call a month later asking you to bring the bike in for a checkover and service to be sure that everything is working as it should.
All of that will be free of charge.
If your Halfords branch refuses to assist request the manager to talk too and keep talking until they give you what you paid for. A safe and usable item.
I've done it before with a friends Voodoo. It was a build yourself one. I built it and the braking was like trying to stop on a polished Wood floor with socks on.. It was not happening. I went with the buyer and spoke to the manager who told the mechanics too sort everything out FOC and do it straight away..
It's unlikely they will refuse to help or fix the issue as it's their liability on a warrenty item.