Poor tailoring

I used to LOVE jane norman, it was my favoroite shop of all time. However, since it has become Jane Norman london, the tailoring seems to have really messed up. I bought a gorgeous white coat that they are selling at the moment in a size 14, and clearly no research has been done into what sort of shape and size a size 14 person is. Not only am i a little chubby, hence the 14, I also have a large frame. This coat has its measurements all wrong, and I know people are different shapes, but I dont see this fitting anyone well. As usual with jane norman nowadays, there are angled shoulders to this coat, which I can deal with, however if you wear the coat so the shoulders of the coat sit on your shoulders, the bottom of the arm holes come far too low, as if they expect me to have arms the same size as around a size 20 something woman! the bottom of the arm holes hang several inches below my 34E boobs! The shoulder width is also far too wide (I am am broad shouldered) so basically the coat looks great, but if I dare move my arms the whole coat shoots up past my ears, which looks ridiculous. I will be taking it to a tailor next weekend, as I do love the coat, however if they decide they are unable to fix this then I will be returning it.
Im not sure whether massively incorrect tailoring is just for larger sizes (by larger I don't really mean very large, from 14 up), but I'm am genuinely really confused about how they go about deciding what measurements to use.....
As I said, I am less angry about this (I have returned many items due to poor tailoring since jane norman switched hands) but more confused about what the heck they are doing...... I really do not understand why they are making gorgeous clothes that simply wont fit most people!