Hi Dave:
Yes, I'm sure they would have been there at the same time. In my grandfather's letter he states that on 14 August 1939 he was responsible for 323 male compositors (and 5 female) at Finsbury, 19 men (and 47 female) in the warehouse and 48 men (and 1 female) packers as well as all the other staff such as printers, binders, folders, watchmen, etc etc making up the 1,404 personnel. A monotype operator was a compositor who used a specific machine, I believe.
My grandfather was on a firewatch rota at the factory during WW2 and although not on duty when the factory was hit, he was phoned and had to dash there to help the firefighting and try and rescue what they could.
He also used to visit the Dunstable plant on a regular basis.
Regards