Hey guys!
Thanks for the great responses!
I already managed to get the drawings fixed to what I needed, and I done with the scale>reference command you's were right
I think what the architect must have done was use true sizes in model space, then scaled it down, then moved it over to the layout space or something, pretty weird! But it's fixed now and I'm working away with perfect scaled references in 3DS Max
Cheers,
Andy