"As for the queer notions of Clarke, Roberts, Ross et al"

I think that's a bit strong - Anne Ross certainly isn't some new-age hippy wafting incense sticks and hugging standing stones - her seminal work Pagan Celtic Britian is still the foremost text on the subject. This is a scholarly work not some airy-fairy new age rubbish.

The discussion seems very centred on the notion the Church was responsible for the creation of the green man, and the Church was responsible for his creation. There is evidence to refute this, and we have to look further afield than Britian to find it. The green man is not confined to the British Isles, he is present throughout Europe, and especially in France and Germany where he is seen in Churches and Cathedrals much as he is in the Isles.

Anderson (1990) states the only green man named in a carving is in Musée Lapidaire St-Denis and appears on a fountain c1200 under the name Silvanus. This god was present in the Celtic pantheon in Britian too where he is called natively as the 'woodland king' (Green, 1986). This god is present both on the continent and here (we know that 'Celtic' culture was distributed across Europe from Hungary to Spain) and he is also named in the French carving. The fact this carving is attributed to the Thirteenth century illustrates the fact a continuity may well have existed between Celitc and mediaeval Europe.

I believe it would be a mistake to overplay the role of the church with regards to it's influence on the core beliefs of the common people. The fact the Christian church used ancient religious sites to build their churches on and adapted the indigenous popluations own festival to their own ends demonstrates their desire to impose their own religion on the population - it's not beyond the bounds of possibility they hijacked the green man and sheela-na-gigs as they have much of our cultural heritage in the past 1500 years. Certainly, when someone carved the name of the god of the greenwood on a stone fountain in France 800 years ago, the churches agressive cultural steamrolling of the deeply-held beliefs of the locals might have have rankled with them too.

Refs:
Anderson, William (1990) The Green Man Harper Collins, London and San Francisco; 111-112.

Green, Miranda (1986) The Gods of The Celts Alan Sutton Publishing Limited; 182-183.