This website is an absolute treasure trove of information about the Marathon des Sables as well as other ultra-races, including very useful kit discussions.
After much research I've now got hold of probably the most important part of the kit: the rucksack!
I've gone for the OMM Classic Marathon 32 litre rucksack which should hopefully be able to carry everything I'll need. Getting it now should mean I can test it to destruction and start using it on my runs!