I agree with Bertie: I'm still breastfeeding 3 years in and I think the "avoid all possible even theoretical risks when breastfeeding" is a messed-up attitude that impairs a lot of people from feeding as long as they want to and perpetuates the idea that bf is only for a few weeks/months.
When you are pregnant your baby shares your blood supply, so if your blood is 0.05% blood alcohol by volume, so is your baby's. OTOH to get that way you've been consuming beverages that are 5%, 12%, maybe even 40% ABV, but that drink has to be processed through your stomach and into your blood in the course of which it becomes far more dilute. So if your baby consumes milk at 0.05% ABV, (a non-alcoholic beverage, as PPs have noted), the amount that actually ends up in their bloodstream is going to be beyond miniscule, probably not even measurable.
The NHS may take their usual lowest-common-denominator advice of don't do it, because that's a legally safe position for them to take, which is understandable but still, IMO, kind of stupid. Heavy drinking and care of a newborn isn't a great idea, but the "risk" of a couple of drinks and breastfeeding is so small that it's basically invisible.