Very common on the Focus of this age, which unfortunately can result in the spark plugs rusting in
![Eek! :eek: :eek:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
Its due to water from the screen washers running back into the plug recesses, and Ford have a mod for it.
![Wink ;) ;)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
Before going any further, see if the coolant level drops. Hopefully it wont, and there can be quite a bit of residual water in there.
Be lucky!
John