British Empire OOB as requested!
Imperial garrisons were normally much smaller than a whole division, and organised into separate battalions. I've generally picked one battalion or regiment from those stationed there to give its name to the whole division, and given its strength as a fraction (based on 12 battalions to the division).
Singapore
Leader: Ridout
0.16 infantry division:
Shropshire Light Infantry
Hong Kong
0.5 infantry division:
Middlesex Regiment
North China (in attack range of Qingdao)
Tsingtao Expedition
Leader: Barnardiston
0.25 infantry division:
South Wales Borderers
# Yes, this is the regiment that fought at Rorke's Drift.
Ceylon
0.08 infantry division:
An Indian Army battalion, name unknown
Burma
1.25 infantry divisions:
Burma Division
(give it an attached engineer brigade?)
India
British Army in India
Leader: Duff
0.75 cavalry division, 4 infantry divisions:
1 Indian Cavalry Division
8 Division
27 Division
28 Division
29 Division
# strictly speaking, these forces were not organised into divisions until after the war started
Indian Forces:
Northern Army: 6 inf divisions, 1 cavalry division
Leader: Willcocks
1 (Peshawar) Division
2 (Rawalpindi) Division
3 (Lahore) Division
7 (Meerut) Division
8 (Lucknow) Division
Kohat Brigade (0.33 division)
Bannu Brigade (0.33 division)
Derajat Brigade (0.33 division)
2nd Indian Cavalry Division
Southern Army: 4 inf divisions
Leader: Nixon
4 (Quetta) Division
5 (Mhow) Division
6 (Poona) Division
9 (Secunderabad) Division
Princely Forces:
In total about half a division of cavalry and one division of infantry volunteered to serve the Empire from the Princely States of India. This might be better represented as an event rather than a force in the starting OOB.
Aden
Leader: Bell
0.42 infantry divisions:
Aden Brigade
Egypt
Force in Egypt (or Egyptian Expeditionary Force):
Leader: Byng
0.08 cavalry division
0.33 infantry division
Sudan
Sirdar Egyptian Army
Leader: Wingate
1.5 militia divisions
# These are Egyptians (puppet troops) not British Empire forces
Malta
0.42 infantry division:
London Regiment
Gibraltar
0.16 infantry division:
Cheshire Regiment
Nigeria
0.42 militia division:
Nigeria Regiment
Sierra Leone
0.16 militia division:
West African Frontier Force
Kenya
0.25 infantry division:
King's African Rifles
# excellent war record so rated as infantry not militia
Rhodesia
0.25 militia division:
Rhodesian Regiment
South Africa
Union Defence Forces
Leader: Beyers
0.5 infantry division:
1 East African Division
# Separate battalions not actually organised into a division until 1915. Also, called "East" African not "South" African because that's where it was sent to fight.
Mauritius
0.08 infantry division:
Somerset Light Infantry
Bermuda
0.08 infantry division:
East Yorkshire Regiment
# join the Army and hope you get sent to Bermuda, not the mud of Flanders...
Jamaica
0.08 militia division:
West India Regiment
Newfoundland
0.08 infantry division:
1 Royal Newfoundland Regiment
New Zealand
Samoan Expeditionary Force
0.16 infantry division
New Zealand Expeditionary Force
Leader: Godley
0.33 cavalry division
# formed as soon as war started from militia units and volunteers
Australia
Australian Imperial Force
Leader: Bridges
1 infantry division:
1 (Australian) Division
# formed as soon as war started from militia units and volunteers
Canada
Canadian Expeditionary Force
Leader: Alderson
1 infantry division:
1 (Canadian) Division
# formed as soon as war started from militia units and volunteers
(I know you said you've already got the Dominion armies, but since I had the information to hand I thought I'd post it anyway as a cross-check on your figures

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