As described, have been into the park today, have to report that progress on the ground to date is nil.
Having walked all round and thought I had somehow missed it, I called the park managers (if interested, 020-7930-1793) and was told that work had not yet started, and that the ceremony was somewhat in advance of things. It appears, from this discussion, that the actual location is
in the north-west corner of the park, at Hyde Park Corner. The memorial will be ready in 2012 as well.
A pleasant day for a walk in the park though. I'll keep up with things.
A bit more here :
Bomber Command Memorial