I don't know what you're trying to achieve.
It's working pretty well for exporting references as OSCOLA so, so far, it's achieving exactly what I was hoping — I was really just wanting to share it, for others who might also need OSCOLA support
The part I explained with less than ideal clarity is rather hard to explain, I think...
My concern / clarification came about because, to make text entry easier, I renamed a user-specified type to, say, "Unreported UK case law (neutral)", and then renamed the fields:when I come to enter a reference, I can tell easily which fields need completing with what.
For example, my field labels for "Unreported UK case law (neutral)" are as shown in attachment 1.

- 1.png (17.54 KiB) Viewed 31660 times
This means that the GUI makes text entry easy, as shown in attachment 2.

- 2.png (68.17 KiB) Viewed 31660 times
When it comes to writing the output bibliography or citation format, everything is as it should be:
where "t" is the case name, and "u2" the neutral citation.
However, whilst I can make these formats available for download, I cannot seem to make the types available for download: someone needing OSCOLA probably needs not just to format information in a particular way, but to capture particular information in the first place (e.g. case name and neutral citation).
Whilst the format I provided will work fine
if someone knows which fields to type the information in, it's not as easy as would be the case if they could download the accompanying types too, and thus be presented with the same GUI that I have.
As it is, they would have to look at the format field order, work out which element equated to which part of the reference, and then make sure they typed in the right box. For example, they would need to know that "t" was "case name", and that, when adding a reference, they would need to put their case name in the "Title" box.