i paid 28 pounds for my back box from a car parts shop and fitted it my self and i got the front pipe from kwik fit for 20 pounds and fitted that myself .they wanted a extra 10 pounds to fit.
A long story, but...
I was ripped off when I had to get one from National Tyres in Chesterfield. They charged £50. I had to take it to my local Fiat guys in Hereford to get it refitted properly. Then sent National the bill! And they paid.