I don't know where the Focus ST is built but the holiday reason is quite likely. Parts can also be a problem as parts suppliers may not be able to keep up with Ford's demand for, in this case, rear spoilers.
I worked part time in a VW Fleet department, and still towards the end of April this year, I was quoting a 10-12 month wait for a factory ordered Golf GTI. As with the Golf GT TDI mentioned above, the delay would most likely be due to the fact that this particular model was updated in May/June this year, so it would be about now that factory orders start to come through. (It has been updated to look slightly closer to the GTI, to separate it from lesser models)
With regard to the Focus, I wouldn't worry too much about the dealer telling fibs. There can be many reason why a car is delayed. (ie: shipping conditions/delay from factory to port/parts etc). I wouldn't worry that your car is in the UK being thrashed by the salesmen, as they have hopefully already had a demonstrator to give them a taster of the car!