OK I have done some more digging around in TNA for information relating to the RDC. I'll post some general information here for future reference for all. There is a lot of information in WO/32/18622 which is a huge file of correspondence relating to RDC re-organisation.
1) I found a comprehensive list of all RDC Protection companies
as at 14th May 1918. They were listed by Command. The commands were: Eastern, Western, Northern, Scottish, London, Irish, Aldershot, Guernsey and Held in Reserve for Ireland.
You can see there was an eye on the "troubles" in Ireland and WO/HS were trying to figure out how to slim the RDC down but keep men for service in Ireland. Some units had already been demobbed by this date and there were plans for more during the coming months. There is an original letter from CICGS Home Forces (French himself) outlining his thoughts for Ireland.
Southern Command is shown as having 14 Protection Companies and 1 Reserve: P.Coys: 251, 252, 253, 254, 257, 258, 259, 261, 263, 265, 267, 268, 270, 271 (missing #s recently demobbed) and 300 in Reserve.
2) RDC Establishment in Round Figures at 5th April 1918
was listed as:
Employed P/W Camps 14,000
Employed Vulnerable Points 8,000*
Employed in Ireland 10 Coys 3,000
Employed in M.I. and Sp.M.Areas 2,000**
* I did see a wonderful memo in the file stating along the lines that, "As no-one has tried anything against these points in 3 1/2 years of war, I think we can re-organise these forces somewhat"
** I saw reference elsewhere to Special Military Areas but I have to assume that M.I. is "Military Intelligence"
These troops were marked as not to be demobbed in the current climate.
3) Statement of Duties and Establishment for Southern Command 31/12/1917
was shown in a letter and attachments:
This was very lucky for me but, sadly, was not replicated for other commands. Anyone who's ever had their butt kicked for being over budget will recognise the tone in the COs letter as he tries to explain why he's 10 Officers over establishment ha ha!
It lists how many officers (with all names and the Station they commanded), No. ORs at each station and they were doing. So, for example, for the P.Coy my man was in, under Major J.J. Forbes-Pelloxfen. OC 267 Protection Company (267's responsibilities are all P/W Camps except one - Slimbridge). , based at Evesham, there are listed:
Strength of Station
I hope this helps someone else in future.
Kind Regards and Good Luck,