Hello jeanba
It may be that the RAF pilots confused the Bf 109 fighters for Fw 190 fighters or that 315 Sqn, RAF engaged a unit other than II./JG 2. The Strength Returns for II./JG 2 show the Gruppe equipped with Bf 109 fighters in May 1943. Here is the link:
www.ww2.dk/oob/bestand/jagd/biijg2.html The only photograph or profile of his Fw 190 with JG 2 that I have seen is of his Fw 190 A-4 "Yellow 1" (W.Nr. 0140 748) in North Africa. Have you already seen that one?
Horrido!
Leo