Castlemartin starling roost - how long has this been going on?

This may be old news, but my first dusk visit to the Corse in a while....after a morning visit to the Gupton side of Castlemartin Corse, rewarded with fine views of female marsh harrier hunting over the reedbed, my wife and I returned late afternoon to walk in along the north side. We noticed flocks of starlings ranging from 50 to a few hundred flying in from all points from E through N to WNW. They were overflying the reedbed and gathering in the fields on Gupton where the cattle are outwintering. The penny did not drop until we were driving back, but looking across from the Angle road at Corston Beacon towards Orielton I could see what looked like smoke pouring down the valley. It proved to be a vast flock of many thousands. Two more similar sized flocks followed in the space of a few minutes. We hastily drove back, passing two sparrowhawks on the way, to the north car park at Freshwater West. Sure enough, in the failing light huge numbers of starlings were flying about over the reedbed. Small groups were still flying in over our heads from the NW. The light was too poor and they were too far away for any sort of count, but I don't think we could have seen a lot less than 50,000. A dusk watch from Starmans Hall (approach from main FW car park) should shed more light on the matter.