In my case it wasn't a Focus, but a Mondeo.

The mysterious creaking noise used to occur if the car had been standing
for a while, or when reversing up my drive. It also seemed worse in the
mornings. I assumed a ball joint was on the way out, but ...

My local garage found that the offside upper anti-rollbar bush wash making
the noise. The bush itself was in perfect condition, but they took it to
bits, cleaned it, put it back together - Not much improvement. But they
suggested that as this was a low milage car (only 18k over the last 8
years!) that it would go away with more miles.

And sure enough, once I started clocking up a couple of hundred of miles
per week, the noise just faded away, never to return.

Weird.

Al.