I'm one of those 5M
I can't begin to describe how infuriating it is being forced into a biometric registration because you absolutely positively must speak to someone at HMRC. Especially when the reason they're threatening immediate court action is because somebody fucked up and put a number in twice. Also, they send out letters demanding action "within 7 days of the date of this letter", and you don't actually receive them until the 7th day. Which in one case was the 31st of January, so you can imagine how much fun that was...
What I will say, though, is if it lets me in when I'm anything short of enraged to the point of spitting then it's probably too lenient.
I accept that they're just trying to do a job that nobody likes, but so many of them are so incompetent at it, or too constrained to be able to help out.