I have seen 2 posts this week. One said 24 hours, the other said 2 weeks! So I guess it is pretty hit and miss. I will be submitting my own application in the next day or so ( also to London) I'm flying in the 7th November and don't feel panicked at all.
If this is the seminar I read about, it is actively selling itself as a way of getting a DTV. However if you look into the site more it will give you a list of embassies which will NOT accept this course as a reason to issue a DTV.