Longtime Expat Contemplating A Return

Two part post. One long, one short.

Part the First

I've been living in the USA since I was 12. I'm contemplating a return to the UK in 2013. I have retained my British citizenship.

As far as I know, I don't have an NI number. Contraiwise, my I've-only-got-Google research suggests that if my Mum got benefits for me (which she did) she would have had to have set me up with an NI number in order to receive it.

Is that scenario possible? Or was something (gasp!) wrong on the Internet?

(I'd ask my mum, but she's dead. Dad - still in America, also - is no use.)

Mind you, if Mum did register me for an NI number when I was a wee 'un, then begins the exciting process of finding out what it is!

I would just cheerfully shrug and apply for a new NI once in the UK, but I have horrifying visions of the system throwing up my name with a number already attached and hilariously awful consequences ensuing. Besides, not having to wait for the bureaucracy to do its thing would save me some time. I'd really hate to get a job offer only to hear that I can't get paid until I provide an NI number and, oh, did we mention the bureaucracy will take up OMGhowlong to do so...

Thoughts? Suggestions?

At this point, I'm honestly hoping that Google led me astray!

(edited for accuracy because I'm a bit stupid sometimes)

Part The Second

Has anyone else around here done something similar - returned to Britain after leaving as a child? I'm curious to hear others' experiences / advice / horror stories, etc.

Thanks!