I got all my stuff from Wemico. Reasonable price and easy to deal with. Just draw the profiles you want and they can supply it.
They did the flashing above stonework, framing around window and the sill, drip profile above window. I used Kytun slate verge. I also had Ali Fascias, can't remember where they came from at the minute. Don't need architect to draw it up, just use a bit of common sense and thought.