Advice and Help Dornier 17Z KG 153 or 155

I am trying to locate a German "Combat Report". Date 12th July 1940, time 15:15 approx. Location, Lyme Regis Bay, flying from Lyme Regis to Portland. I have read three accounts from British sources, with three minor differences in each. One British casulty (Canadian Pilot), Dornier damaged by first attacker. I have found that KG 153 and 155 was the German "Squadrons". It appears that the German plane made it back. I have hit a brick wall, would like help to advance my personel search. British information from National Archives, Kew. Thank you. John