So how on earth would we encourage people to do all the essential jobs that need doing if people didn't need to do them? If you could do nothing for £12k a year why would you work 40 hours a week as a toilet cleaner for the current wage of c.£14k? Or even a nurse on £27k? The only way you could get people to do the essential jobs would be to raise their wages drastically, so you'd have to pay all supermarket staff, toilet cleaners, etc £70k a year. This would either then cause huge inflation and the price of everything would go up, so the basic income would have to go up, and then the wages for essential jobs would have to go drastically again...repeat ad infinitum until you get paid a million pounds to work at McDonalds!
Well, 12k isn't a huge amount of money for a single person. Most people with mortgages, bills and childcare costs wouldn't be able to survive on that for very long. So someone could go to work and earn 14k on the checkouts at Tesco and have a total income of 26k, which is pretty good for a single adult.
The income you get from your salary would be on top of the income you get for "doing nothing", so of course there would be an incentive to work. 1k a month sounds generous but if you have all the regular bills (mortgage or rent, council tax, utilities, food, a car to run, childcare costs to name a few) to come out of that, you don't end up with very much at all left over for luxuries.
What about saving for things like a new boiler, a new car, new appliances? Christmas presents, maternity leave, holidays, new clothes, children's activities, school uniform...you couldn't afford all of that plus necessities on 1k a month.
I would happily go to work to "earn" 14k a year if it meant my total take home was 26k a year! That sounds like a pretty sweet deal to me.