From what I have read about this, it won’t be a zero limit, it will match what the drink driving thresholds are in Scotland.But what you can’t smell is the number of drivers going past that have had a few sherbets. Hopefully they will bring in the new zero limit for drink driving.
Though from this article, where this chap uses a breathalyser, and experiments over a few days with England and Wales current breath test limit, and the proposed limit.
Looking at the article, it may as well be zero, because one pint, and you will be over the limit.