Hey!
Thanks for getting back to me
That's great to at least know where the problem lies. No wonder all that fiddling with the tk2d settings wasn't changing anything
Strange though, I was using vertex snapping for every sprite placement, and would have expected everything to be aligned perfectly.
Perhaps a bug in unity?
Maybe one thing putting it off was "doubling up" the sprites when building up the blocks. i.e. place one sprite, duplicate it, vertex snap duplicate next to original, select both, duplicate, vertex snap the 2 next to the first 2, select the four, duplicate, vertex snap etc etc.
Anyway, will experiment. Thanks for the insight!