Early movement hard to swallow?

Whilst on our way back from Rosslare yesterday on a Sea Trust  ferry survey we saw three swallows pass by, heading west . The fact that we were almost exactly half way acrossmakes it seem unlikely that they were just feeding and anyway they were flying fast and low as per those we see migrating in the spring and autumn. Our Swallows would still probably be able to breed and raise another brood even if they had failed \aza first timeso there would be no real reason for them to give up already. Of course locally many of our first broods fledged a couple of weeks ago. There might be some advantage to moving south for them I suppose... Is it possible some Swallows, perhaps inexperienced youngsters are still arriving? All in all none of the above seem entirely likely but they were certainly going somewhere!