I am hoping that someone can point me in the direction of somewhere where I can look at uniforms of different types of soldiers/ different regiments/ styles of uniform, etc, so that I can find out more about the people who are pictured here.

This one is the first confirmed photo I have of my great grandfather, and my God he looks so much like my Dad! Anyway, the important thing is that I know he served during WW1 (I've seen the medals and have photos of them- they are the standard ones that were issued, and the story goes he was up on a look-out balloon and at some time got gassed), but I can't find him in the WW1 pension or medal records. I would like a little prod about what to do please.
The second one I have no idea about, but it was in the same bundle of possessions. He looks quite important to me, and possibly Navy? Looks like a gun he's holding.
Very grateful for any tips,
Paula
ID:2796