Well I am not the one to say how much your dealer should charge but the part is standard cost across all dealers so the variation in price is in the labour charges so if you go to a dealer with cheaper labour then the price goes down!
If you have a dealer in London for example then this will be much more than going to somewhere like Cardiff or Newport.
I had mine fitted after I had my car so I shopped around dealers.
But you only paying about £25 more than I did just over a year ago so its not bad!! And it looks great!!!
Jones!
PS - My dealer initially wanted to charge me £900 cos they wanted to by the part primed but not painted and then charge me for painting them up....until I found out you could buy them in form Germany pre-painted!!