Red Hat / Fedora :: RAID 6 LVM Recovery From Interrupted Reconstruction

I have a pretty huge (16x1TB disks) RAID6 LVM array on a Red Hat box which has really thrown a spanner in its works and I'm in a right fix: I was part-way through rebuilding the array with one replacement disk when a second died and a third seemed to have fallen from the array. I was replacing a disk which had been showing signs through SMART of probable failure (uncorrectable errors) and I noticed the second disk was just starting to give similar but slightly less numerous errors.

Now my logic based on a gradually growing understanding of the workings of the LVM is that I stand a chance of resurrecting things as the data held on the machine has been static for a while (a few days) before my attempted drive replacement and none of the disks have actually FAILED.

I have replaced the unit I removed so the physical devices are as they were before the exercise. I clearly need to carefully convince the configuration that it's "how it was" and there are a few meta-data files in the /etc/lvm/archive I believe I can use to re-"set the scene". Presently the machine fails to boot completely and it's patiently waiting in single-user mode for my next visit.