The RN was notorious for firing at anything in the air, friend or foe, hence the course change. As for why they didn't turn back, or why they chose to cross where they did, is anyone's guess.
The 464 Squadron ORB is online at:
http://naa12.naa.gov.au/scripts/ResearcherScreen.asp
Put 464 Squadron in the keywords field, click on search. Click the "display" button which appears. On the results page, click on "Digitised Images first". Then click on the "View digital copy" icon for theb "Unit history of number 464 Squadron - September 1942 to September 1944" file. In the window which results, click the "Enlarge" so the entries become legible. I find it easiest to navigate through the pages by entering a number in the "Page" box.
There is a brief description of the operation on page 112, details start on page 116, though the convoy etc doesn't appear to be mentioned.