CAT 1 only (UK)
So, technically, at a CAT 1 only airport there is no requirement for LVPs for arrivals. Arriving aircraft will be limited by their company Aerodrome Operating Minima - if the required visual elements cannot be acquired by minima then the aircraft should execute a missed approach.
However it would still be prudent to have some form of safeguarding in place (e.g. increased arrival spacing, vehicle restrictions, etc) to mitigate the risks of piggyback go-arounds, runway incursions, etc. This safeguarding is likely to be needed long before reaching CAT 1 minima.
For departures, at CAT 1 only airport, there is only a requirement for LVPs when RVR is less than 550m. If LVPs are not in force then departures are not permitted when RVR is less than 550m.
Again though it would still be prudent to have some form of safeguarding in place before reaching those conditions. That way LVPs can be declared in force when required. This safeguarding (reduced arrival rates, stop-bars, simplified taxi routes, vehicle restrictions, standby power supply - for departures when RVR is less than 800m, etc) will need to be commenced long before reaching RVR 550m.
The point at which safeguarding starts will vary from airport to airport depending on the airport characteristics (dimensions of airfield, location of VCR, equipment, etc.).