I was on that cruise about 6 months ago and I signed up for the "Hassan II Mosque & El Jadida" tour. That included a short visit to the Habous Quarter but I don't recall being harrassed by any vendors and the visit to the mosque was marvelous. I try never to book any tours that involve seeing the "Highlights" of any place because those tours using involve spending a lot of time in shops.
I remember seeing a photo of luggage held up in Heathrow a few years ago. Regent passengers on that cruise never saw their luggage until well after that cruise ended. After seeing that photo.... and following the blogs of those cruisers with no luggage..... I've made sure to NEVER check luggage through Heathrow!!!