Cheers Dean, when I went to look for DLC cutters it says "recommended for aircraft grade aluminium" so can't be bad; and the ones from APT are a reasonable price (and very pretty). Struggling to find a corner radius tool at a less than eye-watering price though, but might just do the corners as a separate pass with a non-DLC tool, very little material to remove.
It's interesting to see that the speeds recommended by APT are considerably lower than for a "normal" uncoated aluminium cutter of the same size, I wonder if this is because they're assuming you're machining a high strength alloy??