In the UK you can rent vans to take abroad, but only a few companies have the ability (or desire) to arrange the appropriate insurance. I have done this several times, although only in Europe. Maybe outside Europe will be a problem.
Not sure about Morocco, but did hire a van four years ago from a company in Mijas Costa which a friend and I took to UK. Agreed a special rate (as we were doing 5,000 kms in less than a week!) and no problems. Brand new van, with 200km on clock and returned with 5,600!
If you are still looking, let me know and I will find you the details of the company so you can contact them – they may allow a rental to Morocco, possibly with a large(r) deposit.