On the facelift the auto bits are much better, I never have to fiddle with the wipers and the lights are great; the lights will even come on now if the auto-wipers kick in for more than about 3 wipes which is good, because this was lacking on the prefacelift.

On my old Mk 7 Titanium with the Auto Lights & Wipers the system used to fail quite a lot. I found out in the end it was the connector in the back of the sensor behind the centre interior mirror. There is a connector behind the large bit of plastic which if you pull out disables all the Auto function and the wipers go back to normal intermittent style of lesser spec'ed Fiestas. However it will chime and show a message every time you start the car after about 5 seconds to tell you that there is an Auto Lights / Wiper Malfunction. The chime can be disabled but the message and the orange 'i' will be lit up. The lights, if you leave them in Auto mode will come on automatically when the engine is started as unplugging the sensor makes the car think its permanently dark!

Update.... As suspected, the Halfords/Bosch wipers are too short - went to Ford and got a pair of wipers for a surprising £17 after taxi driver discount (I'm not a taxi driver, but that's what they offered!) , the driver's one is about an inch longer and sweeps over the sensor - problem solved!

Snap them off.