Perhaps the reference is to the production of "In Flanders Fields"? C, B & S took part in the Seeds of Peace concerts in 2002 and 2004, and according to their website, are doing further concerts entitled "In Flanders Fields" this year, being, of course the centenary of the outbreak of WW1.
Oh, and at risk of being rude (what me?), Guest might have found all this if he/she had got the right spelling for Coope. (It has been corrected in the thread title and after Big Al's second post). Just Google (as I did) Standing in Line Coope Boyes and Simpson, and there it all is.
All sounds very interesting anyway.