I read about this film yesterday, an now look at this:
A BBC press release from today confirms that Mr. Lee is indeed part of it:
BBC - Press Office - Poliakoff's feature film 1939 starts shooting
statement from the Director of "1939":
"It is truly thrilling to be making it with such a tremendous cast which combines some of the most exciting young talent in the country including Romola Garai, Eddie Redmayne, Juno Temple, Charlie Cox and David Tennant with such great names of the British film industry as Bill Nighy, Julie Christie, and Christopher Lee."