I’m afraid I don’t have any information other than what I’ve published on here. If you are still nearby the local history section at Lavender Hill library were very helpful when I went (it was a few years ago, so you might want to check first if you are planning on going in case it has moved or has restricted hours).
Looking at your description I wonder if the bomb you mention is this one: http://bombsight.org/bombs/16821/ Unfortunately that site has very little detail and only covers the blitz. You can get a lot more from places like the local archive.
Another site that has a bit more detail (and looks like a real labour of love by the author) and covers the V1s is ‘Flying Bombs and Rockets’, there is a page for SW11 http://www.flyingbombsandrockets.com/V1_summary_sw11.html and there are a couple on there that might be the V1 you saw, you might be able to narrow down based on direction and time.