I've been researching my own family history and it seems I've found a pattern into which corp my Grandads (&GGF) joined. They all seemed to have voluntered at their local Territorial Centre, so my Great GF ended up in Notts & Derbys but GF's ended up in the Arty as the two N&D Battalions had converted to Arty. Guess what I'm getting at is that where you lived altered which corp you joined. So in Nottingham or Derbyshire you be more likely to join Arty but in Notts or Derby you'd more likely join Notts & Derbys (Sigs for Derby). In Leeds it'd have been RTR, Sigs or Arty. Sheffield would have been engineers. Lincoln - infantry.