Cracked it! Took the glazing panel off and two of us managed to shake/tap the dead flies near to a hole in the panell.Many thanks everybody - I will try all of these suggestions - and get some more bungs!
glad you got them all out. what was it like getting the window back into the seal.
Most just lift up further and out once you remove the stays, a look at the top will confirm that is possible.how did you get the window out and was it difficult to put back in