Thanks for Geoff's input! In fact as you mentioned it I could not have been 100% sure of the Hobby either, as the view was distant and fleeting, but the swift-like silhouette was highly suggestive. In any case it'd be safe to say 2 "falcon species"!
For your information, I did see a Hobby close in flight on 10th Nov this year. There were dense breast streaks and the range was around 20m, so I was quite sure it was a Hobby. No photos though!