A few months ago I bought a second-hand Sierra handbrake as a spare and found it had a warning light switch built in. My idea was to replace the exciting handbrake with this new one, a fairly major job as the mechanism under the floor has been 'scrunched' a bit after repeated impacts with the road.
But when I looked closely this morning I saw the switch was actually just clamped onto the handbrake through a couple of indents.
So I whipped out the passenger seat to access the handbrake, checked it and bingo, it had the same indents. So a quick transfer of the switch, wired it into the loom (the existing wiring was already present in the tunnel).
Job done !!
Later: Turned out my original wiring route wasn't suitable as it chafed, so I drilled a hole in the tunnel wall, inserted a grommet and put the wire straight into the tunnel. Much better.