Moverton,
The soldier seated in the centre is regular army, so you can discount him as being yeomanry.
The ones in khaki are either lancers or hussars, the corporal and the soldier with the long service good conduct stripe are in 'blues' with foreign-service helmets. The pugrai around the helmet suggests to me, we're looking at a photograph taken "somewhere east of Suez" to coin Kipling.
I'd guess the time-frame between late 1880's - mid/late 1890's.
Isandlwana
