Umm, DJ1's are both 20mm and 100mm. 100mm in travel and 20mm in axel, meaning you need a special 20mm through axel hub on your front wheel - which also means that the wheel you've been using on your MZ Comps won't work as that is standard quick release.
Personally I think your being ripped off. DJ1's are good but not worth a frame+fork+£50 (they may be "brand new" but he bought them, that makes them second hand full stop), considering you'll need to buy a new front wheel as well.