Gil, It depends on the application but I doubt if either of the above will meet your needs if you are dealing with UK product, especially if you are looking to file the screws in with a correctly indexed slot.
Various UK companies have produced a range of gun pins & screws but I think they have al stopped now: just too much variation.
The closest 'modern' approximation to old UK screws is the 3/16 Whit and it can usually be used without any adjustment of hole. I don't bother with a tapered thread although this is what you will find in 90 % of cases. Parallel threads are just more difficult to screw in but give better strength and cope with repeated insertion into wood better.
If you have a lathe and die you can quickly turn these out (under- or over-size if necessary)with as long a slave head as you need, overall length and ,very important, the right countersink angle to match what you are attaching. This can vary between 70 & 55 deg and needs to be pretty much spot-on if an aesthetically perfect result and/or maximum bearing strength is required.
Make sure you polish the thread with Scotchbrite or similar or any roughness can wreck the hole on removal.
If you don't have a lathe, then find a local machine shop and commission a short run on their auto equipment with a range of different countersink angles but most at 65 deg.
On 2nd thoughts, it is probably cheaper to buy a lathe!
