When you say "early pre-Christian pagan England", are you referring to: pre-Roman pagan southern Britain (ie BC); the early Roman period in southern Britain (pre-Christian pagan, so maybe the 2nd century AD); or the early Anglo-Saxon period prior to Christianisation (so about 500-600AD)?

(Also, I confess I don't at all know what you mean by Teryan)

Checking Wikipedia, I see that the Mists of Avalon is a work of Arthurian fantasy, set during the time of the Saxon invasion. So, then, I'd have thought you'd really want to know how gender-egalitarian post-Roman Christian Britain was, not early pre-Christian pagan England.

Remember that Arthur is a fictional story set in what is essentially a fictional time; very few Arthurian romances portray the period accurately, because the source material (the original Arthur stories) is itself extremely inaccurate (it's portraying a legendary, mythical time, not an accurate picture of late Romano-British culture).

So, at the time prior to the Saxon invasions, what later became known as England (it was the Anglo-Saxons who named it England), was inhabited by the Romano-Brits; a somewhat Christianised, thoroughly Romanised culture. As Christianisation had been recent, it's quite likely that there were still many pagans; however, they were not the "Mother Goddess"-type pagans of Mists of Avalon; they were Roman-style pagans, worshipping gods like Jupiter, Juno, Mercury, Venus, etc (though sometimes with British names; for example, Bath was a city where people worshipped the goddess Minerva/Sulis, using both a Roman and British name).

That doesn't directly answer your question about gender-egalitarianism. But I want to explain the background. Arthur is set in a fictionalised, mythical golden age. Many modern works try to set him in a slightly more realistic time, before the Saxon invasions. What they often miss, however (as I think Mists of Avalon does, but then, it is just a work of fiction, it's not trying to be history), is that the pre-Saxon period was the post-Roman period, nearly half a millenia after the Romans had conquered Britain. In some medieval legends, Arthur is related to the Imperial family of Rome. So, it's a mistake to think about gender equality or other cultural sociological phenomonen at this time as being about Brythonic culture, but rather, as being like Roman culture.