The Kiel Hafenkurs wasn't used before July 1949. This is from a report of that first event (my italics):
Zur Eröffnung der Kieler Woche veranstaltete der Kieler Motorsportclub Nordmark (ADAC) das überhaupt erste Motorrad- und Wagenrennen in der Fördestadt.
At the opening of Kiel Week, the Kieler Motorsportclub Nordmark (ADAC) organised the first ever race meeting for motorcycles and cars in the 'Fjord City'.
The two- and four-wheeled meetings I know of in Germany in 1946 are:
28.04.1946, Mühldorf / Inn, Trabrennbahn (Motorräder)
26.05.1946, München (Dante-Stadion), Aschenbahnrennen (Motorräder)
14.06.1946, Reutlingen Straßenbahnrennen (Motorräder)
16.06.1946, Stuttgart Aschenbahn-Motorradrennen (Neckarstadion)
21.07.1946, Ruhestein-Bergrennen (Motorräder u. Sportwagen)
11.08.1946, Gr. Preis v. Braunschweig (Motorräder in 3 Klassen)
18.08.1946, Stuttgart Aschenbahn-Motorradrennen (Neckarstadion)
08.09.1946, Neuwied (Motorräder Solo bis 250,350,500 ccm sowie Seitenwagen bis 1200 ccm)
29.09.1946, Karlsruher Dreiecks-Rennen (Motorräder u. Sportwagen)
27.10.1946, Tübingen Aschenbahn-Rennen (Motorräder)
27.10.1946, München, Großer Preis von Bayern (Motorräder)
Possibly also in Ulm and Vilshofen.
Oh, and contrary to my previous post, the Braunschweig event was in the British zone.
Regarding Miles' war service: I only know he was in tanks, but somewhere there will be operational diaries which - providing you know roughly (ideally exactly) which unit he served in - it should be possible to trace his whereabouts. As I mentioned there may be unit newsletters too. Could be in a regimental museum or the National Archives at Kew.