Hi greatbeanbags
I sure if any of the following info is wrong someone will say
To be an Acting/Corporal is what it says he was acting as a corporal, this happened before the soldier was promoted to full corporal and recieved the paid to go with the rank (the pay bit might be wrong)
A corporal's role varies between regiments, but in the standard infantry role a corporal commands a section, with a Lance Corporal as Second-in-Command . When the section is split into fire teams, they command one each.
Until 1961, lance-corporal was only an appointment rather than a rank, given to privates who were acting NCOs, and could be taken away by the soldier's commanding officer (whereas a full corporal could only be demoted by court martial).
A section is a small infantry unit first introduced in the British Army. A section generally consists of about seven or eight soldiers, with a junior-NCO as commander. This would mean that your Grandfather would of lead soldiers into fighting.
Timberman