~S~ Best of luck with this!
Some thoughts:
I'd recommend using one of the excellent sceneries already available for the underlying 'landscape' - Steve Mclelland's European sceneries are great for this (available here - CFS2 scenery pages 2, 3 & 4) . Provided you set up the airbases.dat file up correctly, you should then be able to use these in the Mission Builder.
Then either create your own air base/beach head sceneries using something like Airport or FSSC and EOD, or have a look around for some ready made mission builder objects. For example, this looks like it would be very useful:
http://www.simviation.com/cfs2misc12.htm - Atlantic Wall bunkers
I'd love to hear how this goes.
You might get some inspiration from the GroundCrew's Hurricane campaign - which covers part of the RAFs operations over Dunkirk -
http://www.groundcrewdesign.com/cfs2pack.htm~S~
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