The guy says that he is worried about having his trim pulled about, so telling him its easy to hardwire it himself is a bit naive. It is easy if you understand car wiring circuits and you have a multimeter or some other tester, if not the deal seems good. Halfords is no better nor worse than some other stores or workshops. All work on a car is hit or miss unless you personally know the fitter or know someone who has had work done there. Even then it can be a bit hit and miss. I had a Thinkware f750 front and rear camera fitted under a free fitting deal by a firm that fits and maintains fleet telemetrics. instead of getting the 3 wire hardwiring kit he wired it by cutting up the powe plud r lead, 2 wires, It ran 24/7 and over wrote everything every 4 hours. I now do my own.
There is only 1 bit of trim to remove to hardwire a camera and I am sure that it would be difficult for a fitter who has done no doubt many Next base cameras to mess it up.
Talk to Halfords and express your concerns and go for it.
If you do it yourself or get a mate to do it, it's fuse 13 for ignition and 21 for continuos power.