The blokes laying with Bren at the back of on Bisley range in the plotos are from the East Surrey Regt. Re the video. Notice the small boy standing in front to the left of the Bren. I bet he got an earful! The blokes firing the Bren off the tripod at the end of the video are using a trials ZB gun (note the vents in the flash eliminator*) and are staff members of the Small Arms School at Hythe (or Bisley where it moved in June 1940.
* We decided against the vent holes in the flash eliminator and had to pay royalties for the privilege and opted for the stepped flash eliminator instead. Alas, without the vent holes there too gas 'rings' soon formed and the now disturbed escaping gas (don't forget that it's travelling faster than the bullet at this stage of the game.....) was causing a high proportion of the bgullets to become unstable. So we reverted to what the canny Czechs suggested in the first place........ A straight narrow taper!