Great post
@Pretty Mouth , detailed and relevant.
It's unfortunate you didn't join with a scheme a few years back after completing your course as you would have been accepted. Page 28 of the EAS document then says it is permitted to accept new QS from existing schemes, although there's a load of 'and' and 'ands' required!!
I have kept the spec of my EAS domestic installers course which specifically says it meets the requirements to become registered (at least it did at the time, I don't believe it would now as it is level 2). However, If you really need to become registered then I would contact each of the bodies and ask them all if your qualifications are sufficient. Hopefully you have something in writing with regards the spec of the course which says it is, basically get as much ammunition as you can.
If that fails then I guess you have 2 options, ask
@telectrix (discreetly) for as much info as possible about how he still installs CU's, new circuits etc without being registered. Do the level 3 course, not as difficult to access as it may seem, there are on line courses I believe, with a small amount of classroom attendance required (ask
@happysteve as I think he did one).