UPDATE: Tell me if this is a 'thing', because I might otherwise just be off my rocker, but I think the floppy drive (and Floppy Emu) issue I was having (intermittent connectivity, and failures to get a system installed) were down to the floppy drive connection. Basically, I replaced the HDD in one of my problem Macs and the issue persisted despite the Floppy Emu and system disks operating fine on other machines. So, I had suddenly ruled out the hard drives, the floppy drives and the Floppy Emu as possible culprits leaving only the motherboard or the floppy connections/cables as sources of my woes.

So, I took the cables off, swabbed the leads with a 99.7% isopropyl alcohol solution and then went about connecting and disconnecting the cables to the sockets on both the motherboard and floppy drives numerous times. I booted my Performa 630 and had zero errors with data transfer off my Floppy Emu after that. Is it possible that there can be a bit of a 'build-up' on these connectors? Or, at the very least, they need a bit of tweaking after sitting dormant for so long?