As far as I can make out the Martini problem has almost been solved. It is still out of scale with the figure itself and the length between the first and second barrel bands is way too short.
This figure doesn't appear to have a collar badge so not sure what regiment it is supposed to be but the hat does remind me of an illustration in the Zulu War book from Osprey by Angus McBride. In that book the illustration shows two 'old sweats' from the 1/24th in patched up uniform, given the duration of their overseas service, with one wearing an old beaten straw hat. This looks more like an enlarged boater or if anyone else remembers the UK Goth band The Mission, it looks like the lead singer, Wayne Hussey, minus the sunglasses!
Given the accoutrements this is 100% a soldier from the British Army and not from one of the volunteer forces.