Just a thought, but have you tried getting hold of a copy of the Squadron ORB for the first half of 1940?
The squadron still has an active Association with a website
www.74squadron.org.uk , the Secretary Bob Cossey can be contacted on
secretary@74squadron.org.uk , perhaps he could help to fill in some of the blanks.
Whilst on the subject of the 74 Squadron ORB for this period, I did happen across another aviation forum thread that quoted passages from it, so there are definitely copies of it out there. Unfortunately my e-mail to the individual concerned hasn't ellicited a response thus far.
Regards,
Ian