Well the wording isn't clear (I only have CAA BTW) "must not act as flight crew if they are undder the influence of alcohol or a drug" though 20mg/100ml seems to be the limit (compared with 80ml/100ml for driving). Also remember the 8 hours bottle to throttle rule.
P.S. after drinking your first drink one hour will elapse and from then on 1 unit of alchol will leave per hour.
P.P.S its probably best not to risk it. A pint 10 hours before the flight is probably OK though.