there was a program on tv around xmas where they put so many people to the test as regards amounts drunk and it did vary considerably from person to person. One guy drank 5pints and was still within the legal limit, the presenter was put on a test track and fed either bacardi or vodka & coke over a period of time, after a so many drinks he could hardly keep the car on the track, again he tested under the limit !! it was a real eye opener..
as buildersmate says there is no correct limit..just dont risk it if in doubt