Grif, do you know the control called table index which is placed to the right of the actual contacts column, very close to the edge of the screen? It used to be possible to locate that by directly touching it and then swipe up or down on it to quickly move from one group of contacts to another, sorted alphabetically by their first letter. This stopped working sometimes around iOS 8, I believe. Fortunately, just moving to headings on the rotor and jumping around the contacts this way still works as always and it has exactly the same effect.
Lukas