I'd go for urban myth. I have Hugh Verity's book in front of me, 'We Landed by Moonlight'; Secret Landings in France, 1940-1944. A war-time history of Lysander Ops if you like. There's a very detailed index with all departure airfields mentioned, and many diversions. Not a single mention of Heigham Holmes.
Hugh Verity - Wikipedia, the free encyclopedia