It is not so much driving in the Sahara as getting covered to visit certain countries in the Sahara.
In the UK the Brit govt's FCO travel warnings
to certain places like Mauritania, Algeria and northern Mali can technically render your insurance invalid in the event of a claim.
Other European govt agencies give IMO more accurate assessments of the real risks, notably France
, so you may like to try and get insured there. All being in the EU you'd think that would be allowed, but who knows, maybe you have to be a resident.
I would try Europ Assistance
, a French company with the English-speaking arm based in Ireland (last I knew). Used them before for blacklisted countries, as well as World Nomad
(Australian). Campbell Irvine (similar to HB) seem to have lost interest last time I asked.
Then again, it is possible HB (who I've also used in the past) ignores the FCO stance, but that is unlikely as it requires too much investigation to make a decision on where FCO get it right and where they go too far.