We are touring Morocco and hope to be off road as much as possible, i expect it will be dry sometimes rocky and need to do a fair bit of tarmac. I have read much about marathon mondials being the tyres to get for touring with a mix of road and off. does anyone have any experience of them off road? what are their limitations? they don´t look so good for english mud but should be dry in Morocco.

Take a look at whileoutriding, Cass Gilberts blog, he has a couple of reviews of the Marathon tyres and rates them quite highly.

26er ?

If so, I can heartily recommend Specialized Hemishpere Armadillo's
http://www.specialized.com/gb/gb/ftb/ci ... -armadillo

I had a set on my touring bike a few years ago and did several thousand happy miles of road, dirt road and dry tracks on them. No Punctures. The tyres were still on it when I sold it on.

I've done some Scottish on/off-road touring on Mondials. They are surprisingly effective in a range of conditions (though they struggled in soft snow).