HI Ian,
I cannot accept that the Shipwash lighthouse was the culprit either. If we assume that the Orfordness light is almost 100 feet high on a ness that is 4 metres above sea level and viewed from the forest it just shows itself through a cutting in the woods at Gedgrave then the Shipwash lightship would need to be significantly higher than the lighthouse for it to be seen above the Suffolk landscape.
Regards
Schooner