Thanks. Decided I should go with the actual geometry that will be used rather than the box which I was using to practise. I've been running through the tutorials again to get myself back up to speed on organising the roof tiles but constantly tying myself in knots. No matter what I try I cannot recreate the attached image.
I've created new geometry, a diamond along with a 'tile and a half' according to Creating Roofs with RailClone tutorial to allow the offset. I've wired it to a transform and Array 2S as per your file. What I can't grasp is how to interlock the tiles with a slight overlap to produce the effect in the attached image. Adjusting padding with negative values won't overlap when it's wired to a sequence.
Any help would be very much appreciated, I seem to be going in circles. Stripped version of the scene attached also - reset most of the values as it's become a mess.