I’d say that’s a golden eagle, in silhouette you won’t see the white tail of a sea eagle anyway, but the slightly longer tail, and those rather distinctive notches in the trailing edge of the wings near to the ends, compared to the sea eagles wings which are almost perfectly parallel right to the ends seems pretty conclusive.
That’s also a way of identifying ravens in flight, their wings have a sort of notch in the trailing edge, and a longer, kite-shaped tail compared to carrion crows.
I’m deeply envious of you seeing an eagle, although I may have a better chance of seeing a sea eagle now that there’s an active re-introduction programme going on on the Isle of Wight.