This seems a fairly clear "extraordinary circumstance" with no delay compensation due.
Although calling in may be a good proactive idea, BA would, like most carriers, handle the reroute either while you are enroute to LHR or upon your arrival.
Nothing in your post suggests anything beyond careful attention to the safety precautions required after an airplane is struck. They can be extensive and frustrating, but quite welcome when you are FL over the Arctic Ocean.