Because the production of the first Harry Potter movie was top secret, KnowWonder's request for onset photos lead to blurry photos coming back to them that were unusable. This caused them to send one of their devs named Phil to the set in order to write down everything the set designers did with all of the locations and the team then proceeded to base their environment work of their game solely off of Phil's writing and memory.

They also based the environments off of the heavy research they did on old and medieval British Architecture.
Contributed by PirateGoofy