Yes for the twitter... but with my "large" audience, I won't go far ;)
A twitter from Joel or Jeff would be much appreciated.
Here is an example of email you might consider sending
You are receiving this email because you did initially registered to SO DevDays London 2011. As you know, all DevDays were cancelled (http://devdays.stackoverflow.com/)
However, a smaller "DevDays London" is being organized by some Stack Overflow member and might interest you: - one afternoon - same day than the original venue (Monday, 14th November) - at Canary Wharf (not far from the original conference center) - a much smaller price tag ;)
You can see more details (and register if you are interested) at http://www.meetup.com/DevDays-London-2011-Plan-B/events/33387912/i3/socialmedia/
Note: a post on Google+ would also help (I have posted on my page, but again my social footprint is quite small)