I reckon it's a buzzard too - red kite have quite distinctive white areas on the underwing, which I can't see in these images. The middle image clinched it for me - the bird seems quite 'heavy' set, compared to the red kite which look quite delicate in comparison.
That's my guess, anyway
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p.s. know what you mean about the 'classic black blob against the sky' - story of my life when photographing birds in flight
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Thea