Interesting stats from the ONS about moving from adolescence into adulthood and the modern markers that have changed over the years.  In a nutshell:

Moving into Adulthood

18 Adulthood
19 Starting full time work
23 Moving out of your parents home
27 Moving in with partner
29 Having a baby
32 Getting married
34 Owning your own home

You can read the full report here: