The issue with UBI is that no one really understand how much it will be.
the only realistic uk proposal was from the Green Party which set UBI at about the state pension rate, or circa 6K a year. Additionally looking sites like RSA or Basicincome.org and Looking at the numbers and understanding the subsequent proposed changes to tax it is in effect saying that we will do away with the initial tax free band and give you the equivalent in cash. This largely washes its own hands and gives a UBI of circa £3k a year.
Speaking to the man in the pub there seems to be a perception that UBI might produce an income of circa 20K a year, or 'how much might i need to live comfortably without working'. There is a big difference between those two numbers.
My other concern is that wages will normalise and , after a while, drop by the amount of UBI. to put workers back in the position they were in prior to the introduction of UBI (Though that naturally happens if its simply the withdrawal of the free tax band)