just found this post searching google and I have the exact same issue with my focus ( 55 plate ). I have come across quite a lot of similar problems with other focus owners but your thread is the first of an exact match. Would you be able to say exacly what sorted the issue as I would rather have a go myself before spending hundreds on labour alone and possibly weeks without a car. So far I have removed the instrument cluster and cleaned the printed circuit board like some sites suggested. While refitting the cluster I noticed the lights going mad when i lightly touched the wiring loom that connects to the cluster ( via a connector ). I was wandering if you could confirm if any of this sounds familiar with you and if your cluster issue is now history???
This is a known problem of the Focus MK2/MK2.5 instrument cluster. The problem is caused by bad soldering connections of the connector to the circuit board. The soldering connections become cracked due to vibrations. This results in an open connection of 1 or more pins of the connector.
Many times the problem can be solved by resoldering all 32 pins of the connector to the circuit board. You just have to disassemble the instrument cluster to remove the circuit board. Now you can heaten up every soldering connection of the connector with a soldering iron with a small tip. I repaired several MK2/MK2.5 instrument clusters this way. In my opinion it is definitely worth a try.
I had this problem before, but a local garage recommended a company to me which cleans up and repairs the circuit board and gives a 2 year warranty for about £100, saved me paying out around £700 for a new cluster!