Failed effort to find my Great-Grandfather's World War I service record

My Mum's paternal grandfather, James Burns, served in the British Army in the First Word War. We know he joined up at the outbreak of the war and that he survived all the horrors of battle - though he was wounded in the head with shrapnel. We do not know what regiment he served in, or what battles (if any) he fought in. Neither do we know his number or if he won any medals. In fact we know very little about his service record.

I used Ancestry.co.uk to try to find him myself, but with no luck. James Burns was a very common name - I did find one report showing the details of 35 (Yes - thirty-five) men whose names were James Burns that were killed in the war. Horrific.

At the end of last year I engaged the very helpful folks at http://www.fourteeneighteen.co.uk to do a professional search for me. But alas - they could not find him either despite their exhaustive searches. An extract from their report for me is as follows:

The Royal Irish Rifles at the Battle of the Somme
(1st July, 1916)  - Image link to Wikipedia.

The absence of a service record means one of the following:

1. His record was destroyed or lost (by far the greatest probability)
2. He carried on to serve in 1921 or later
3. He served in one of the Guards or Household Cavalry regiments (unlikely)
4. He did not serve in the army
5. He served under a different name.

Many records were indeed lost due to fires and the recycling of paper due to paper shortages. There is also the possibility that name he used when joining up was different from that which he used normally. His name used in the 1911 was "James Burns" - see census return here. The census form states that he "Cannot read". Somewhere along the line "Burns"changed to "Byrne" which is my Mum's maiden name.

It is believed that James Burns died in an asylum in 1925.

I'm not sure what I'll do next - but I will not give the search for his service record.