Thanks to all for the extremely helpful replies. I have now found his army service record on Find My Past and this shows that he served as a gunner but only from Nov 1893 to Dec 1894. He was originally a volunteer with 22nd Middlesex Rifles and he joined the RA at the age of 19 yrs and 2 months. His attestation documents show that he had received a "notice" from a Sgt Jones, 3rd Battalion, Royal Fusiliers .. (does anybody know what this means?). His short army career was ended by an accident when his leg was broken in three places by a horse. He was medically discharged with a small pesion.
After he was discharged, though, he did go to Ashanti (1895-6) and in his book "To Kumasi with Scott" he documents in great detail the departure from Liverpool on SS Loanda on 30 November 1985 with "officers and men from the Army Service Corps and Engineers, also a detachment of Artillery", and the entire expedition from landing at Cape Coast on 18 December to the surrender of Prempeh and the return trip in early February 1986.
So, my question is .. in what capacity was he part of the Ashanti expedition?
Was he there as a war correspondent? (I think that , at the age of just 21, he would have been too young for this - and he had no experience or track record)
Or could he have been there in some sort of non-service role for the army or the government?
Or was he some sort of early "Indiana Jones", seeking out and writing about his own adventures? (and if so, how did he manage to get official clearance and authority to be so intimately involved with a military action?)
Maybe somebody on the forum knows how these sort of "arrangements" were managed at the time ??