For any doubters out there, the standard Buhlman tables which give 3mins @ 6m and 14mins @3m are valid from 0-700m. That's level 2 territory (and level 3 on a bad day). I've done some digging as my Bulhman's aren't to hand, but there's a copy here:
Look at the bottom right and you'll see the altitude range they're valid from and to.
A table that is valid up to 700m (the Buhlman table Axeman quoted) is always going to be more conservative than one that is a sea-level table (BSAC Level-1). To make a fair comparison you need to compare the tables that are valid at the same altitude - ie BSAC level 2s.