This is fascinating to me. We don't have tracking like this in the US, it would be really cool to be able to look these numbers up.
Of course, when we take a car off the road we don't have to report it, we just cancel our registration and insurance and that's that, so there's no way of knowing how many permanent garage ornaments are out there. We do have a titling process, but once its titled in your name, that process is over until you transfer ownership.
Our version of your MOT is quite different as well, and varies by state or sometimes locality...It seems like your program is generally more strict than most states, but I like that you are given time to fix "advisories".
It seems like this helps you keep cars on the road longer in general by forcing you to fix the issues before they go too far, but on the other hand it seems to force a lot of cars into early retirement for people who cant or don't want to fix the issues. I'll bet your junkyards are full of great cars that didn't have to be there.