Many thanks for all the info, I think I will go with 64x 260mm spokes as advised by mboy as makes sense. I know that their isn’t much gain on having the cx ray spokes, maybe a little stiffer and more longevity, I already have DT super comps on some other wheels and was going to get those, but this is my dream build with CK hubs for my MTB so looks are coming into it as well, I know its vain but I will only buy this sort of build once.
If your interested (but your probably not!) I’m going with silver alloy hubs, black bladed spokes, silver brass nipples and black ZTR Arch rims.