I'm gonna second what he said except the disk power cables, I found them on Aliexpress and ebay pretty easily. Granted they take weeks to ship from China but they do arrive and do work. Also, I'm using SSDs in mine and just have them stacked up in the disk area. Not secured at all. If I feel like they need to be, I can velcro them in later. If I were using spinning drives, I'd plan on something different however.My experience is with the quanta windmill
1) UK 240v will work fine.
2) Each side has one power and sata cable. If you need a second the power cable will be difficult to find and there isn't really a place to put more than 2 drives total (1 for each half).
3) Yes each half can be powered up independently. Small red button on the board is the power button. When power is applied they return to last state (turned on when power removed they will power on. Turned off when power was removed they will not power on).
4) RJ45 can be used as standard NIC
5) No one that I have seen has SAS working.
5 again) On the one that has the riser it should work as long as the power draw isn't excessively high.
6) If you want to run Windows or an OS the requires the newer features then get the Quanta. Are v2 CPUs worth the cost? (I got the cheap $55 2670v1) If not it shouldn't matter.