Managed to find the instructions and the floor is in 4 sections, 6 joists per section.
I've ordered 48 joist supports, 2 for each joist on each section.
Will have to build it from the back forwards I think and level as I go, won't fasten the sections until is all level and sturdy.
Looks like a bit of a pain but worth the effort as it was just dead land and I need the storage space!.
View attachment 156704