Welcome to Rootschat and to the Armed Forces boards!!

First of all though, I'm a little confused by your post!!
May I ask where did you get the Regt details from?? Have you confused a number of medal cards bearing the same name??
It all appears somewhat garbled to me I'm afraid!!

Are they "family oral history"??
5DG did not become "Inniskilling's" until 1922 when they merged with the 6th (Inniskilling) Dragoon Guards.
It is such that a number of cavalry squadrons of the Regt became dismounted and fought in the trenches. They became mounted again towards the end of the war and they did not lose their nags fully until they became mechanized with tanks in the 1930s.
You may find this interesting...
http://www.rdgmuseum.org.uk/history.htmPrincess Charlotte of Wales' (Royal Berkshire) Regt were an infantry Regt in their own right as was The Rifle Brigade
https://www.thewardrobe.org.uk/royalberkshire.phphttp://www.greenjackets-net.org.uk/rb/branch.htmIt is highly unlikely that he could have been an artillery instructor with either Regt as they were both infantry, and did not have access to the large guns of the artillery. The Royal Artillery themselves dealt with them, esp field guns!
Do not be confused by the "Brigade" bit of the Rifles...It was a "normal" Regt!!
As for the Middlesex Regt...They were an infantry battalion, and in WW1 the machine gunners were transfered to The Machine Gun Regt.
There was a machine gun bn of the Middx in WW2, 1/7th bn "The Die Hard Gunners", some int on whom can be found here...
http://www.freewebs.com/middixgunners/history.htm If you could be kind enough to post everything you have (places of birth etc) and from whence you gleaned your int, we can help further!!!
