Seems to me that when these companies were mass-bubbaizing no4s, you could buy the flashider and wood seperately. Perhaps some enterprising gunsmith in a shed somewhere undertook his own bubbification program to try and raise the price of the once common #4s to jungle carbine levels.
A cutoff barrel with no crown, and a pot metal flashider, do not sound like the quality control levels that any military would accept, especially Royal marine gurkha navy commandoes. And the story about the CFC lady knowing anything about these guns is even more incredulous. As to the markings no4 and a half, it is more likely that to get the wood to fit the rifle, it was easier to remove the brazed on tang for the trigger and replace the lower floorplate than to modify the wood to fit a mk2 modified rifle.
I think PT Barnum had an expression attributed to him for a buyer who goes for an incredulous purchase:
http://www.historybuff.com/library/refbarnum.html
But not even he could foresee a guy driving 100 miles to do it a second time.
Anyone who would fall for this should be wary of emails from Nigeria requiring your assistance to help retrieve some corrupt officials stash of loot.