Hello Peter,
The CWGC has this on S/L Peacock:
Flight Lieutenant (Pilot) Michael F. Peacock, RAF 90124, 601 Sqdn., DFC, age 28, 20/05/1940, Arras Communal Cemetery, F
As the initials and the date of death are the same, I guess this is the same man as the S/L you mentioned. Have you any idea why the CWGC has him listed as member of 601 Sqdn.?
Regards,
Bart