Mate my girlfriend works there and has recommended you go elsewhere.
Im no audio expert and SOMETIMES the fitting is OK, however I would go to a specialist audio supplier or fit yourself.
OFF-TOPIC: a manager recently, at the halfords branch where my mrs works, put a car battery on the wrong way round and shorted a BMW, cost Halfords £3k to fix.
Just my opinion dude
LOL my Dad did that when we were jump starting my car. I have never Jumped so far out of my skin. Luckily i still had hold of my side when i put the wires on and stopped the connection before any major damage was done.