johnjosh43,
You're quite right about the cable 'problem'.
It's not even typical to Concorde.... airframes are aluminium, while the control cables are steel, so the expansion factor is not the same, and the same problems exist even in subsonic aircraft.
The problem is solved with 'cable tensioners'.
Unfortunately I have no drawing instantly to hand. Maybe some other reader here does, and can post it.... if not I'll try and do a sketch from memory and post it.
As said, the problem is/was much older than Concorde, and we just 'borrowed' from existing technology.
And of course, the expansion differential, and the length and flexibility of the airframe, were some of the reasons why Concorde went for 'fly-by-wire', or - as we called it at the time - 'electrical signalling'.
CJ
PS And yes, there was deliberate 'slack' in the electrical wiring, and also various arrangments of expansion joints in the fuel and hydraulic systems.