I came across this post looking for solutions to the same problem... Thanks for all the support on here - my two Drayton valves were also the wrong way around (no arrows on the body, had to look in the installation manual)
I found this post as I was also confused about the ABV from Tower, which I bought at Toolstation... I fitted the valve, and then ordered another to see if both were "broken", before calling the manufacturer to ask how it works! :S
So.. in summary:
The inner black dial has geared teeth on the...