As long as you are only having a ‘symbolic / non-legal’ wedding party then you require no papers at all.
If you want to get married in the Catholic church then you have to prove that you are Catholic and this is done by having your home church send a letter to the catholic church in Marrakech to confirm this.
What is not possible is to have (like in UK) the registry book signed at the church.  In UK people either go to the registry office on the same day to do the legal stuff or they have the registrar come to the church to have this signed on the spot.  This is not possible in Morocco.

What most people do is to do the registry office bit in UK at home a day before going out, then have the wedding ceremony in Morocco.  Legal date of marriage will be that of the registry office bit (on the marriage certificate).  Most people are fine with that.

Jewish weddings are different as the rabbi (orthodox only in Morocco) provides his own wedding certificate (called a ‘ketubah’) which can then be registered in another country as a legal proof of marriage.  Some people bring their own rabbi (easier but more expensive) but Morocco has some rabbi’s but this is more complex as requires preparation etc.

Muslim weddings can be legally provided for but the paperwork would have to be verified to convert this to a UK marriage certificate. It depends whose authority you are interested in having etc. Residency is not an issue although if you are French then you can get married at the French consulate in Marrakech.