Approach Ban
I just sat my IR initial on Friday, and this was one of the points I discussed.
The approach ban is 1000' agl. The approach may continue if after the aircraft passes either 1000'agl or passes the FAF and the RVR drops below that required for the approach (as published or 800m for single pilot ops - whichever the greatest)
Cloub base is never a show stopper, only the RVR/met viz.
Hope that clears it up
ADRH