Uniform Identification please (early 20th century)

[CV-S]

Good morning,

I have attached a photograph of a relative born in 1875, born in Hertfordshire and grew up in Surrey. He is said to have served in the Boer War and the First World War, and it is believed this photo was taken during the latter. I have very little to go on, and his name is very common (Smith) so I can't pin down any army records. I'm hoping if I can get a uniform ID it may help be trace his army record.

(added: Ernest is the seated man, but both seem to be wearing the same anyway)

Any suggestions or observations greatly appreciated 

[mmm45]

Can date it after 1918 and before 1921  as the lad stood up has 3 overseas service chevrons they came in in 1918 and both dont have medal ribbons that were issued bu 1921
No obvious regiments though the lad stood up has shoulder titles and is a Sgt the lad sat down is a Corporal

Ady

[CV-S]

Wow, I'm amazed at all that information you could get from the photo. It just shows what having an expert opinion can give.
Thank you very much Ady