My wife's Fiesta on 03 plate has similar probs. Having seen the Watchdog item on Focus instruments, we suspect that her problem is the same - bad connection at multiplug behind the inst. cluster. In the case of the Focus, it seems to be corrosion, causing a bad contact - some people have even used WD40 to clean the contacts, and solved it.
Worth a wiggle on the wiring?
Look at www.bbc.co.uk/watchdog
Jim
Jim.
Jim Gould, April 2008