Nskeates,
If 'wiggling' the wires makes the warning light go off you're getting a spurious supply/ return.
Your handbrake switch allows the circuit to be made so if you've replaced that it would point to a fault with the supply cable.
It may be trapped in trim or chaffed against an adjacent cable.
The chances are its within the short area you're moving.
Are you able to see the cables or are they loomed/ taped together?
Look for a crushed area or a shiny wear area.
A torch and a small mirror are good for inspecting
