@ Pen-y-gors
"how often do both drives in a RAID setup fail at the same time? And with a dodgy backup?"
if its that important then you need to pay more for a more resilient solution, perhaps active / standby cluster across geographically separated data centres provided by different vendors on different ISP's and supplied by different power stations. what's the cost to you of the outage vs the cost of a resilient solution?
regarding BT, yes this latest outage should not have the impact on its network that it has. Services should have instantly rerouted with little to no impact on end users.