Nigel Cole - director of Doc Martin said on a fan page about the Lighthouse filming! --
"He thinks the lighthouse is something he is most proud of. 5 different locations. Lizard, Godrevy (only from the sea) port Gavern, a set in the studio (yes where the electrocutions happen) and a cliff top near PI. They shot MrsT and friend against green screen and inserted them in shots taken from a helicopter. The government authority withdrew the permission to film at Godrevy the week before the shoot".