Osprey?

I saw a strange sight today, from my car, as I was driving through the small village of Arddleen.  A large bird was being mobbed by a number of smaller ones;  nothing too unusual about that, I often see such a thing - usually the large bird is a buzzard, sometimes a heron, a great black backed gull, even a red kite.  This bird was none of those, that much was clear from my car, but I can't be sure what it was.  My best guess, though, is osprey:  something about the shape of the head and the markings, but it was such a brief view, and I had no opportunity to stop.

The bird in question was certainly a raptor, and ospreys are passing through at about this time of the year, though I suppose the present very wintry weather has to make it less likely that one should be present:  surely any osprey with half a brain is going to have halted its migration, faced with wall-to-wall snow and biting winds.  So I feel this has to be filed away as 'unknown', or at any rate 'indeterminate'.  Pity;  an osprey at Arddleen would be a very special tick!