Honestly, probably none of that but when I went it was £250 fully fitted for a cat back, the car was an MK3 Astra running a C20 let and getting original ones from the Cavaliers and Calibras wasn't an option so it was all I had really, nothing off the shelf fitted or simply couldn't afford it. I completely agree with what you're saying and they probably know nothing about other than how to bend, weld and fit, but it did the job quite well.
But given most exhausts for the clio are not cheap they are a good option, if you can afford top end then go for it, but given he's bought a 2nd hand one it seems he isn't willing to splash out on top end stuff.