Yes machines and computers do have faults and do break down, however look at the causes of aircraft accidents (in peacetime particularly). The biggest cause factor is mainly human error, whether that is aircrew or supporting staff.
It will be a long time before people are ready to trust their lives totally to a machine without having a pilot monitoring it with the ability to take some form of control; but look at how automated the systems of the modern airliner have become.
WEBF yes it would appear Duncan Sandys was a little premature in his beliefs but that is hardly an argument against UAVs. A UAV does not have to have full remote control all of the time - it can be programmed to carry out a loss comms procedure.
"Personally I don't think UAVs will ever be as flexible as manned aircraft. That is due to basic facts like the fact the Earth is curved."
The earths curvature is not an insurmountable obstacle - look at the likes of Global Hawk which certainly go considerably beyond horizon.
Yes jamming can also be a problem but again not insurmountable and especially against a low-tech adversarywho doesn't have much if any capability.
"Well sort off......in that you can send less data."
How much data do you need to send to fly a UAV - not much I would wager. And where reduced bandwidth would make real-time recce more difficult again it would not be as difficult for a manned ac?
GB