Hi Cameron, actually all is not lost.
See the medal card index: next to each award is the reference number to the MEDAL ROLL index. These are separate files and are not online, but can be found at the National Archive at Kew, London. These can be viewed in person, or better still, pay a researcher to pull the files for you. The medal rolls were complied at Regimental level and these will give you his Battl.
However, bigger units, like the RA, RE etc will often not have the details in place. Like all written records, they are only as good as the person who writes them up. I did this research on my Grandad's medal roll index through a reseacher and it cost under £15 to research two entries, which gave me photocopies of the two pages. As my Grandad was RA sadly the details to his exact unit were not included.