Thank you, cats and kittens - I'll get to those tricks in an hour or four after attending to some items on my wife's "Honey do" list.
The motherboard has six SATA sockets on the board, and two on the back panel - and it came with six SATA cables to plug into them. The case advertises itself as being able to carry up to 12 HDD's - and there certainly are sufficient power cables dangling from the power supply.
The first four "devices" were instantly recognised and configured by the power up - but attempts to install the OS onto either of the HDD's were declined until I had formatted them.