Everything is now working perfectly, apart from the mains power connector sticking out of a PCI bracket. For now this will do, it is better than cutting a hole in the back of the case that I later no longer want.
Some observations I have made are that it is quite top heavy at the moment- if I had more time I may consider creating a mount in the bottom of the case to place the hard drives in and also the airflow isn’t particularly that great. I have no intake fan at the front and so the hard drives are running slightly warmer than they should do. The mesh look of the case also means dust can quite easily enter and settle inside the case. I’ve been researching ways to stop this while not reducing air flow and a recommended solution is to use a stretched pair of tights.