Hi, this may help and I suspect that these are the people you are after. The Captain McNeil I'm currently researching myself and would love to know more about him. I suspect he is the father of your Border Horse man. Note those are entries from my database.
McNEIL Archibald. Zulu War 1879; On 1.2.79 53 Cape Volunteers arrived from KWT raised in Dordrecht under Captain McNeil; these men joined the Frontier Light Horse. He is probably the same man that served in the Durban Volunteer Artillery.
McNEIL Archibald. Trooper, Border Horse, Anglo-Zulu War 1879. Trooper, ‘Right’ Wing, Kimberley Horse, Gun War (Basuto War) 1880-81. (Cattle prize money 1882). On 4.1.83 there was correspondence from the AAG Cape Forces in relation to a medal for the Basuto War. Anglo-Boer War; Lieutenant, 2nd Battalion, Cape Peninsula Rifles.
McNEIL Archibald. Carpenter and Builder, De Beers, Kimberley c1885. Son, Archibald served in the CP c1885.
McNEIL Archibald. Born Scotland. Enlisted (Kimberley) 21.2.85 (Age23). Constable, (Kimberley, District NoVII) Cape Police (No133). Discharged 18.11.87.
McNEIL Archibald. Lieutenant, Artillery Company, Durban Rifle Guard. In 1868 he left the volunteers with ten other gunners who formed the ‘Gold Exploring Company’. In October 1868 he had travelled with his party into the Western Transvaal and had received permission by Lobengula to prospect in Matabeleland however his party including himself became ill with fever and returned to Durban. In January 1869 his commission was cancelled for leaving the colony without permission. In 1869 he along with other urged the government to form a Volunteer Artillery Company. Lieutenant, Durban Volunteer Artillery 7.7.70. Captain and Officer Commanding, Durban Volunteer Artillery 19.4.76. Captain, Durban Volunteer Artillery, Zulu War 1879; Durban defence works.