Sann: Not NAF, ARBBL clash.
Joe: Also not allowing all 24.
Sann: True, but it didn't get that far

Even if HadrielCaine allowed the Slann team (which I strongly recommend by the way) it still wouldn't get sanctioned.
It is unfortunate he choose the same date as mine, but he's not the first (for example, Lemf added Snotbowl(?) to the calendar without checking to see if it clashed with anything, meaning I either made ARBBL non-NAF, didn't run it or moved it [to Feb]) and I doubt he'd be the last.
Unfortunately, checking the calendar for potential clashes is not always the first thing on an organisers mind, and some won't know where to look in the first place. And the UK calendar is very full.
As I said above, I wish him every success, and hopefully if he runs it again next year it won't clash with mine or anyone elses (as it is, with the changes made I would have been interested if not for the obvious reason, as I can get to London without needing a car or lift).