mistake - I should have asked Southdown for maounting brackets, but didnt so had to make my own. They are basically enlarged "P" clips i had in the garage, and bolted through the gutter.
I had to drill the snorkel pipe to fit them securely, but if the water ever gets there it will be the least of my worries!!!!!!

pipe emerges straight through wing - the wings are easy to get off so I just jigsawed the holes when I wanted them. The outer wing hole is more elongated front to rear to allow the pipe to turn a bit tighter and stop the pipe sticking out too far