LVP
The JAROPS 1 definition of a LVP take off is when the RVR drops below 400m.
Each airfield may impose their own criteria which will will be detailed in their own MATS part 1. This should also be reproduced in the national AIP. These are normally straight out of CAP 168 but this is only a recomendation based on ICAO annex 6 which is in itself a recomendation, not legislation.
When operating to foreign airfields crews should check the relevant national AIP as there are national variations. For instance the Italians specify that when the airfield declares Cat II/III operations both aircraft and crews must be suitably qualified even if actual conditions are inside Cat I limits. This is stipulated in their AIP and I only discovered it after landing at an airfield which had declared Cat II in Cat I conditions. I was lucky enough to receive a free quality check of both personal, company and aircraft documents!!
The JAR-OPS rules are included in JAROPS 1.440 to 1.460 and their appendices, including the traiing requirements. They are too large to paste here but can be viewed online from the JAA web site.
For private Ops the airfield/national rules apply.
What ever you do, do it carefully!!
MM