Thanks Gerry
The Air Britain book mentions the Intelligence Photographic Flight and the date 3.3.1941 when their three Hurricanes were absorbed by the 2 PRU.
I can't explain their specific dates (either 17.10.1941 and 3.3.1941) but it seems unlikely to have been taken out of the blue, especially since the details were changed from the first edition where it was stated that the 2 PRU was formed on 3.3.1941 by re-naming the Intelligence Photographic Flight!
Some other document must then be the basis for these specific dates and also for giving details about the Marylands.
Your document mentions both October 1940 and March 1941 so we are on the right track...I guess....
Cheers
Stig