Keith noted that there is a disclaimer on their drawings to the effect “do not scale these drawings only use figured dimensions”. All of our construction drawings have this disclaimer on them. All of our A1 plots are plotted “Extents” (in paper space), so the finished plot may well be close to 1:100 or 1:50. The exact scale of the plot is irrelevant so long as there are enough figured dimensions to enable the bluntest tools in the box construct the building, slightly unfair, but you know what I mean.
For our own use, we frequently produce a set of A3 prints as desk copies as they are easier to handle than A1. Some contractors will also request A3 prints for the same reason.
The best example I have of a contractor trying to scale prints was a ground worker bringing a dirty soaking wet handful of near pulp and claiming that he could not set out the foundations from these prints!