I have come over a ridge and found myself in a melee of model aircraft at Membury, which was not NOTAMed. It seems that it's all down to how professional the club is - there always used to be a near-permanent NOTAM for model flying at Henstridge (and of course the unmanned captive baloon at Pershore, which was NOTAMed for about 20 years continuously but I never once saw it).