You can also spend too much time optimising a relatively rare use case. Each of those steps require that you fill out a form and mail it off. The exception is registering for an NI number where you actually have to book and show up for an interview. That's it. You'll be prompted to do each when necessary, there's no benefit/penalty for doing each too early/too late.
In contrast to Finland, where each of the cases above require me turning up in person. Had I just needed to mail off a form, it wouldn't be so much an issue.
