Can I come?
Don't know many of you but this sounds like a good idea.
I can even put up someone for the weekend, if they want. Possibly two people, but that could be rather cramped in my flat.
BTW, IMO the itinerary seems a bit ambitious. I reckon it would be far better to meet in an easy place centrally and then find a pub. Anyone wanting to do other stuff can easily do so once everyone's met up.
I know London pretty well so if anyone needs any help or advice about transport, places to stay etc, I can help.