I was told by an IO at Gatwick not a month ago that if your spouse is present with you in Immigration, you can join
either line. This means he can join you in non-EU as well. I had no clue about this until last month when, upon returning from a trip to Germany, the IO asked me where my husband was and I pointed past the barriers and said 'Oh he's been waiting over there for 20 minutes!' IO laughed and waved DH over and explained to us that since we are 'family' that we can go through immigration together, through either line.

Though not sure if it that's standard in other countries as well...
With regards to your NI number, once you're employed, your employer will give you a temporary number. Then call up JobCentre Plus for an appointment for interview. It's about 6 weeks to receive your number by post.
Congratulations btw. x