Very interesting information about the Luftwaffe can be found in the PRO files of Air 40/1 till 40/2722. These are the Intelligence Reports and Papers of the Directorate of Intelligence from the Air Ministry.
See
www.pro.gov.uk/finding/default.htm
Air 40/45 contains the report of crashed Luftwaffe a/c in the UK and found during the campaign on the continent in France, Belgium, Holland and Germany. There was one report from Greece. The all had a stamp from the Air Historical Branch with number IIG/132/3 in it.
Jaap