I gave it a go on the word of an internet stranger... it is incredibly tight, I can just about get the screw to the bottom of the carbon fibre but it's stripping the paint off the screw and there's no way I can get get it all the way down the length of the screw. My allen key is just about snapped from the effort - I can't apply more force!
Have emailed Modelsport to see if I'm doing something stupid or need to buy something else.
I had 5 minutes to buy a plastic backup off ebay last week, ended up getting a Carnage one which doesn't fit the Vandal/Vantage - re-ordered a 3rd (!) now first class, not quite convinced it will come before Christmas!
Thanks for your help. Have a great Christmas everyone.