... I'd overlooked the minimum speed and this is likely to rule the event out as an "official" AUK event. The DIY option might be the only one up for grabs.
There are only two categories of events "recognised" by AUK.
1) Events organised by an AUK Organiser, or by AUK themselves, within AUK's general setup.
2) For non-AUK events, ONLY events that are listed in the Calendar of RM events produced annually by ACP.
This calendar includes events from all over the world, though under 'France' it doesn't generally include FFCT events, good though they often are. There is no AUK mechanism for 'appealing' to have a non-listed event recognised.
Now, I can't actually find the current RM Calendar online and the printed version is hard to find too. The printed version used to be replicated in Arrivee each year, but that stopped when an online version became readily available.
Registering it as a DIY then riding the event would contravene the (currently unwritten) 'no concurrent events' rule.
I've ridden several of the BC-MF series of events (long time ago) and they are wonderful classics. The most recent ones I did were split into three, time-wise - Tourist, Randonneur and Vedette or some such. The Tourist version split a 200+ -ish mountainous ride over 1 and a half days, by all accounts a good time is had by all, at the overnight accommodation. The Randonneur version is the classic wee small hours start, with the first mountain ridden in darkness, a snake of red lights to follow and a good long day in the saddle. The fast version starts around 6am, and with a 7pm finish cutoff makes for quite a challenging ride. Of course all three groups tend to tackle the last mountain together, which with 2000+ riders makes for a great atmosphere.