I now have William and Anna's marriage certificate. Unfortunately I have not heard of the witnesses before, but it does say that William's father was another William and that he had been a Lieutenant in the 99th Regt of Infantry. I know William Jnr was born in Tipperary and i have found that a 99th regt of foot was raised in that county but was disbanded. The 99th seem to have been appeared and disappeared several times. I can't find anything on Ancestry nor on the Imperial War Museum site, which says a lot of early service records were destroyed during WW2. I'm guessing that William senior would have been serving around the time of his son's birth and maybe up to Waterloo.