A huge thanks to Subliminal Cuts over at TrueAchievements for finding this gem. Someone called Bryan at Video Games Made Me Do It (VGMMDI) has created videos for getting all areas, collectables and secrets (including all codes) which have come in very useful for finding everything I've missed.
Originally Posted by Subliminal Cuts
Here is a video walkthrough of each area, it is a complete guide with 100% completion on every section/area of the game.
The videos are brief whilst still containing all of the information needed, sometimes you will wonder what door he went through but if you play them with sound he will describe what he has done in the commentary
Note: The videos order aren't the order he has played them for some parts and this does become a problem in the windmill area when he has a key that we don't, simply carry on with the other videos and come back to that area at the end, you will get more keys in the later videos
On the last guide called the three cities there is a combination that you need to enter to get the last anti-cube, leave this until you have all 32 golden cubes to stop the achievement glitching.
Here's a link to the playlist: http://www.youtube.com/playlist?list...7&feature=plcp
Each video covers a different section so that you can just jump to the ones you're missing, though if you can't get to an area/through a door that he's shown, you might need to backtrack in case you've missed anything (e.g. lowering the water).