Seems as of late a few of our Focuses have spontaneously developed C/L Problems.
The C/L Module is in the drivers side footwell, it's a black box with yellow plugs.
Due to it's position expecially in the winter it gets damp.
Pull out the plugs one at a time (try not to get them mixed up).
Check the plugs for any corrosion, if there is any then scratch it off.
Regardless if theres any corrosion give each plug a small squirt with WD40 and plug it back in making sure you lock it back inplace.

I found 4 wires that had a white crusty substance on it.
Since going this my central locking has been 100%