A while back I e-mailed the Spanish tourist authority, asking if it
was possible to visit Penon de Velez de la Gomera, Penon de Alhucemas
and/or the Chafarinas. I've appended the replies I received, since
they might be of interest here.
From various tourist guidebooks, I've gleaned that a rough track runs
for about 5km from the road-end at Cuatro Torres de Alcala to the bay
at Badis, opposite Velez de la Gomera. I presume this is the grey
line marked on the modern map at Marcel's site. Some sources indicate
this is driveable, others that a walk is involved - so I guess it's
accessible by 4x4 only.
This seems to be confirmed by the photo at lower right on
http://teleline.terra.es/personal/fgotor/fernando3.htm
there's a helicopter on a landing pad (which I think must be on one
of the lower crags of the island itself), and beyond that is (I
think) a car with a windsurfer on the roof, parked on the sand-spit.
In the background, some sort of road switchbacks down from higher
ground to the spit - interesting that it doesn't skirt around to
arrive on the flat ground at Badis Bay, to the left of the photo, but
this route is confirmed by the grey line on the map.
Letters appended - the first was the original reply to my query, the
second adds information about Alhucemas.

Grant
========================================================
Dear Grant,

I have been told that it is quite difficult to reach the Peñón de
Vélez de la Gomera as there is no means of transport to get there.
Anyway, if you are interested in visiting it you need to contact
the "Comandancia militar" (the military authorities there) in order
to ask for permission (Tel.: 0034 952 684 446). For the Islas
Chafarinas you need to request a permit from the "Ministerio de Medio
Ambiente. Red de Parques Naturales" (Tel.: 0034 915 975 567; fax:
0034 915 975 400).

I hope this information is useful to you.
Kind Regards,

Charo Alonso
Press Department
Tel. 020 7467 5505
Fax. 020 7486 8034
E-mail:charo.alonso@...
(press.london@...)
===============================================
Dear Grant,

For the 'Peñón de Alhucemas' you need to contact the military
authorities as well.
Best wishes,
Charo