Sorry, don't know how to paste a link. Here is info from NHS Direct:
However, research shows that occasional drinking, such as one or two units once or twice a week, is not harmful to your baby while you are breastfeeding. Drinking any more than this can cause problems, such as affecting the mother's 'let down' reflex (release of milk to the nipple area). One unit is roughly equivalent to half a pint of regular beer, a 25ml (pub) measure of spirit, or a small (125ml) glass of wine.
Alcohol clears from the mother's blood at a rate of about one unit every two hours. If you do decide to have a drink, it's a good idea to wait for a couple of hours before breastfeeding. It can be difficult to predict when your baby may want to feed, so some mothers plan ahead and express milk beforehand for special occasions where they may want to have a drink.
Moderation is key - drinking anymore than a couple of units at a time can affect the baby's development and reduce your milk supply. Small amounts of alcohol pass into breast milk, making it smell different, which may affect your baby's feeding, sleeping or digestion. To be on the safe side, some women choose to avoid alcohol altogether while they are breastfeeding.
I drank occassionally whilst BF and my DD are all ok!