Unfortunately GCHI El Hierro is no option.
No fuel and no custom available.
La Palma GCLA has it both and it’s 760 NM from GVAC but recent volcano eruption can ruin your day especially with turbine engine.
I flew into El Hierro and flew into Atar in Mauretanie but wander if this is a good time to go there. Indeed, no customs at El Hierro.
I flew from Dakar over Nouakchott, Morocco, Spain back to France 5 years ago.
We catered for our own permissions (not without peril I must add).
See here:
http://www.abeam.be/back-to-africa-full-8-day-trip-report/
Hope this helps
There’s an article about 270 Polish tourists being trapped in Morocco, because of border closure, airlines not getting landing permits (in polish)