I understand that Peter jackson is having a number of full scale Lancasters built to use as ground props.
As for flying Lancs then take a look at these images made some years ago now.
First CGI models without dirtying down and other detail. Dan Mayer from Canada is the artist.
And he has, IMHO, incredible CGI talent. None of these images are anything to do with the movie. Wrong Lanc for starters.
And some of his 'reality' pics. Spot the deliberate mistake with the Mk V Spitfire...
All the above by Dan Mayer. Credits on imdb.com
With people like this available at Weta Digital, Peter Jackson's CGI company, I am not losing sleep over how the Dam Busters will look. It should be superb.