Rachel Cot bolt nuts

Massive long shot I’ve got the Rachel cot/bed from John Lewis second hand however, I’ve lost some of the bolts. I’ve found the manual and it says 18mm bolt nuts, I ordered them and they’re too big to fit into the holes. Does anyone have this cot and know what size the bolts are?🫣🫣🫣 John Lewis aren’t any help as I didn’t order it directly from them!