1600 a month was far too much, thats more than I got when I was working 6 days a week, that was 10 years ago tho.
a better option would be £1000 a month, but rather than handing it out to specific people, would work better if all income was taxed, rather than 20% of anything over 12k or whatever it is
that way 12k to live on means you can subsist if you are in a terrible job and want to leave etc. or if one person becomes housewife, then their 12k means less spending on things like meals etc if they are at home...
when me and mrs were both working full time, it was often easier to pick up chips on way home, suddenly an hours wages gone for the day.
with 12k being enough to live on, but not too much, theres still reason to work, and as any work income is simply on top.