Hello Romilly and Ceeoh,
This thread's probably getting a bit long, so I'll recap the various sources of information available.
Guides- TNA have a guide to sources useful for family history researchers;
guide 104- I've also put some of the same sources with a bit more information on TNA's Your Archives website;
Metropolitan Police Records of ServiceSources- I have uploaded transcripts for some of the Registers of Leavers onto the Your Archives - links from above link. All of the Registers of Leavers can be found on
Scribd.
- There are more of the documents detailed on the Your Archive's page on flickr, which can be found by there
collections.
Using sourcesSo far on the Your Archives website there are only the first nine of 13 books of Registers of Leavers. But the information about how to use them can be found
here. Otherwise I would recommend using the Scribd link above as it has all the same information that you can use to find the appropriate photos on flickr, should you choose to.
Hope this helps, BarnabyP.
If this doesn't help just let me know.