Having heard back from everyone except Mads and DSM, I was able to draw up this availability chart. Highlighted in green are the most likely "go" dates - there was nothing that worked for everyone, unfortunately, so I've picked dates that are of the most minor inconvenience.
As you can see, then, the most likely date will be August 26th-28th.
I will allow a week for people to give amendments. After that, if there are no objections, I am fixing the date on the weekend of the 26th.
This is the blank availability chart. Green = Available, White = Tentatively Available, Light Grey = Tentatively unavailable, Dark Grey = Unavailable.