Hi WB, I've found the choice of artificial not to be too critical.. If there's a good fall, then the trout usually get fixated, as with Mayfly, Heather fly, Hawthorns etc... and as with the aforemntioned the fish lose the plot too!

Presentation first, then colour a close second... fiery browns and browny oranges do the trick.
One of my best patterns for a Slodier fall has always been a Fiery Shipmans buzzer with black breathers. Fiery/Ginger/Orangey Hoppers are another obvious choice, then Palmers in the same colours.