A number of fields are either having imposed (or are self-imposing) limits in line their SMS Safety Cases.
Cranfield is an example that was debated here a while ago. They have elected to impose a departure RVR limit of 800metres. The justification is that the airfield perimeter is not secure and therefore it is wise to impose a restriction that gives the ATCO some reasonable chance of verifying that the runway is unobstructed before clearing an aircraft to take-off.
It seems to me though that this is all a bit heavy handed. If a field drops below its published minima (and there is nothing wrong with having them), then it should become unlicensed, and the risk and liabilty is assumed by the aircraft operator. I feel this strongly for departures. Arrivals at a VFR field like Blackbushe is a rather more difficult call.
Charlie.