Jim,
Here are a few thoughts to start with. The uniform is (I think) infantry of the line, full dress, about 1870 or 1880. It should be worn with a belt (see the belt support under the right arm and the marks on the tunic.)
The chevrons at the top of the sleve mark him as a sergent; the crown above as a staff Sergent. The crossed flags probably mean that he was part of the Regimental Colour Party (ie the flag with the battlehonours) so was probably known as a Colour Sergeant. This is further supported by the sash, another indicator of a Senior NCO in a Colour Party.
The jacket is roughly the same colour as the sash, so it is most likely a red / scarlet colour; the trousers are a darker hue, so probably dark blue. This with the uniform arrangement of the seven buttons on the tunic / jacket would normally indicate "infantry of the line". It is unlikely that he is in a support Corp (ie Engineers or Artillery).
The Crossed rifles at the cuff usually indicate that the soldier is a marksman of some kind. The crossed flags above the chevron have the cross of St George, so this is an English Regiment (ie not Scots, Irish or Welsh). The collar and cuffs are a light colour, which can indicate a regiment such as the Buffs ro the Grenadier Guards, but this is not a statement that this is the regiment!
Any chance of a close-up of the buttons, the collar or epaulet insignia?
Rod