Aweek before giving the speech, we shall fight on the beaches, what news did churchill think he would be sharing with great britain?

That he would be reporting a terrible defeat at the hands of Nazi Germany. The British Expeditionary Force was cornered at Dunkirk and it looked like they were going to be captured by the Wehrmacht, but the Wehrmacht halted their offensive giving time for most of the soldiers to evacuate to safety across the Channel back to England in what would later be called the Miracle of Dunkirk. Even though the BEF couldn't stop the German invasion of France, their evacuation was still seen as a morale raising victory.