The F1 wasn't a bad bit of kit when you knew what is was for (CQB and snap shooting) and used it accordingly. They were fun to use on the 'sneaker courses'. Most shooting with it was done in the same manner as depicted with the Owen Gun on post 1 -- butt tucked into the armpit, with the upper arm 'clamped' tightly into the side.
One has to remember that the Owen was a contemporary of the STEN and Austen which, in the early days had a wee problem with feeding 100% reliably. The whole idea of the top loading magazine was to gravity assist feeding and to facilitate going prone.
The Armalites pretty much replaced the F1 for infantry scout use before the change from SLRs to F88s.