Doyle; many thanks, your tutorial worked a treat.
Haven't quite worked 'how' it has worked, but I seem to have ended up with some additional XMP files with the suffix 'original' at the end of them. Perhaps Exiftool is being friendly and making backups of the originals?

To clarify (if anyone else is having the same issues) this was my process;
1 - Download and install exiftool FOR MAC (There is a specific Mac OSX package)
2 - Prepare/move CR2 files and .xmp files from Magic Lantern in one folder
3 - Open Terminal
3 - Enter the coomand as Doyle explained above;
exiftool -Exposure2012+=+*.** /drag folder here containing cr2's and .xmp'sWhere the *.** is enter the amount you want to set
eg 0.05, next to the number you have chosen
Too the left is +
+=over expose
-= under exposure
4 - Allow process to run (New/backup XMP files were created for me. I waited until the list had finished)
5 - Select all CR2 files, open in Adobe Camera Raw
6 - FILES SHOULD OPEN, DE-FLICKERED
7 - Select all, make White Balance auto. (Unsure about next bit?...)
Make any edits should you want them? Note, that if you change exposure now, you'll undo the de-flickering!
(Perhaps edits should be done first, then you start the de-flickering command afterwards? Needs testing!)
8 - Close Adobe Camera Raw
9 - In After Affects, import the first CR2 image, select 'Camera Raw Sequence.' Create timelpase!
Many thanks Doyle! Maybe this Mac step by step should be added to that top post/tutorial thread?