For views of the 15 approach try the golf course, or the footbridge at Marston Green Station. The lane off the A45 which led to the field giving good views of the 33 approach and threshold has been closed for some months. You could try the indoor viewing area in the terminal, or alternatively the long stay car park.
I believe that Concorde will be on the Western Apron(old terminal) and will be available for viewing by invited guests only. You should still have a good view from the spiral steps.
I hope that this will be of some use.