a high quality 1k watt psu is recommended more for max overclock, if you are going to be doing that.
the samsung 950 pro m.2 is being released in a few days, that would be the one to get.
32gb of memory would generally be recommended over the 16gb.
depending on your project, the gtx 980 ti may be overkill for premiere, but will be welcome in color apps like speedgrade or davinci resolve and should help with neat video.
disk setup looks fine, if you have room you could place the cache on the m.2 drive too, but shouldn't make much difference either way. make sure the 3tb hdd is not seagate.
Alternatively there is this 12 core mac pro 5...
Apple Mac Pro 5,1 Workstation (12 Core, 24gb ram, GTX 680 for Mac)(TOP SPEC) | United Kingdom | Gumtree
Noted on the seagate and ram. ill be able to get the 950 pro m.2 in the system, just will have to wait until nov 2/3rd to order. which isn't a problem.
the 12 core mac should be slightly faster, but if you run into an application that doesn't multi-thread properly (can happen sometimes with adobe apps), the faster and lower core count of the i7 will perform much faster. gtx 680 is about half the speed of the gtx 980 ti. all of the mac hardware would be older tech, like the ddr3 memory. no m.2 but might be able to use m.2 to pcie adapter or pcie ssd like the intel 750.
One serious warning: The 3TB Seagate Barracuda is the worst disk in it's class. It has by far the highest failure rate of all conventional 3TB HDD's. Much more reliable is the HGST Ultrastar 3TB disk or the Seagate Constellation Enterprise disks. For the rest, see New System Build - Choosing the components.
Probably just throw in a WD Black and be done with it to be honest.
Here is what im going to order... next week.. (if your loading the link on mobile the site is weird, scroll it downwards) http://www.scan.co.uk/3xs/shared/0848af8b-1927-4d13-82bf-6114e01c54f2
Corsair Carbide 500R CASE
Asus X99 Motherboards [Asus X99-Deluxe USB3.1, Intel X99, DDR4, ATX Motherboard]
OC Intel Core i7 5930K Unlocked, Haswell-E, 6 Core
Corsair Hydro H110i GTX cooler with dual SP140L fans
32GB (4x8GB) Vengeance LPX, 2666MHz, CAS 16, 1.2V
4GB EVGA GTX 970 SSC ACX2.0, 1190MHz GPU, 1664 Cores, 7010MHz GDDR5 + OC for £30 extra
850W Corsair PSU
512GB Samsung SM950 M.2 NVMe PCIe SSD (the one being released/stocked next week sometime - it says VNAND on the chip) -
512GB Samsung 850 PRO - 550MB/s Read, 520MB/s Write, 100K IOPS
4TB Western Digital Black WD4003FZEX, 7200rpm, 64MB Cache
Microsoft Windows 10 Home 64-bit
Total cost is just under £2500 inc Vat.
Thanks for your help
Still the expensive and noisy Corsair Hydro, instead of a silent air cooler like the Noctua.
If you plan to go for a high overclock, like 4.8+ GHz, to justify the Corsair cooler, then you need a 1000W PSU.