Xero,
I wrote a small script to fetch the figures directly from the database, without involving FA at all, which allows me to create monthly (Swedish) VAT reports, and also generate a balancing transaction.
The fact that it is done well outside FA may be a problem, but in my case it's rather an advantage since it can easily be run from a cron job. Also, the balancing transaction has to be processed (in my case using curl) by the "Import Multiple Journal Entries" plugin, but that is not an issue since I already happen to use it to import daily sales figures from a web server.
There isn't much "programming" involved. Just send a few queries to the database and assign the results to the appropriate fields, before outputting an XML file. (I'm not at all sure if HMRC will accept files for upload, so you might just want to print/email the report for someone to enter the figures on the website. The same might apply to the balancing transaction, unless you already happen to have some means of importing it. Or feel adventurous enough to insert it into the database yourself. As for me, I was quite happy not to have to go down that route.)
Most of the work is actually mapping your accounts (or combinations thereof) to the fields on the form, so you shouldn't have to be much of a programmer to create something similar. Besides, any language would do as long as it allows you to access a MySQL database. (PHP does have the obvious advantage of running on any server that runs FA, though.)
I'm all for doing it "properly", but this just might point you in the right direction for getting something up and running before that happens.
And, for what it's worth, the wiki doesn't make sense to me either...