Just discovered
this book on Google Books. It's called
The Magic Square: Cities in Ancient China by
Alfred Schinz. If I'm honest I'm sharing it here more so I can find it easily at a later date but from what I've read so far it seems a well sourced and well informed book. I haven't heard of the author but it's retailing at about £170 on amazon which is normally suggests that it is an academic book of good standing!
EDIT: After reading the section on this book that is relevant I have had to utterly re-think my Luoyang geography. Not all this information comes from this source, I'm also using information from some of Rafe and Leowe's work!
It appears that the main walled city pretty much just contained the Palaces, the court, home of some important officials and Hostel's for travelling dignities (and presumably the Capital Hostel that He Jin lead the Norther Army to during a YT scare). This area was guarded by the Emperor's own guards.
Meanwhile outside the 'main city' were lots of walled districts that others lived in, some were nice villas whereas others pretty much sound like shanty towns. To the North and South of the main city were two garrisons with the Northern Army in (separated to prevent any one individual being able to concentrate too much military power in to their hands). Also in this area were the markets and shrines etc. this area was patrolled by the Red Guards.
Anyone know anything/any sources that affirms or detracts from this layout? I'm wondering about emailing Rafe to ask for some clarifications as I'm not 100% sure by what I've surmised.