Christianity in the roman empire.

[Jona Lendering]

It seems that many British Christians did not stay true to their belief though, and they may have embraced paganism as they may have embraced the Anglo-Saxon language at some point.

I think it is possible to exaggerate the distance between Christianity and Paganism. Compare today: there are people calling themselves Christians who teach utterly unChristian ideas (cf. the criticism of the movie The Last Temptation of Christ, which at times turned into docetism), and there are people who are not recognized as Christians but who propose ideas that might fit well within the scope of Christianity (e.g., certain pacifist movements). Nowadays, it is hard to define who is a Christian and who is not.

The same applies to Antiquity. The official Church will have regretted it when a Christian sacrificed to a Pagan god, and the priests will have thought that the sacrificer had "gone Pagan", but that does not mean that he himself was of the same opinion. He may have thought that it was prudent to both attend Church and sacrifice to a local deity. I think many people accomodated themselves to the dominating point of view, and privately kept their options open.

There's a parallel in Judaism: although many people in Palestine of the third century accepted guidance of a rabbi, the archaeological evidence proves that they also used Dionysiac motifs.

I am reminded of my grandmother, who, when my father was recovering from an illness, gave him a big piece of bread before he could go to church. "But the priest has said that we should be sober!" my father objected, to which my grandmother replied that priests don't know anything about illnesses - those were the things only mothers know. We have no written records for the ordinary people of Europe in Late Antiquity, but I am quite sure that they would have understood my grandmother.

Also notice that many bishops (e.g., Sidonius Apollinaris) were not really orthodox. We must abandon strict dichotomies and accept that the phenomena are deeply ambiguous.

it seems that a monk called Gildas was by the early 6th century still able to get a classical education.

In Gaul or Ireland (depends on the hagiographer); not in Britain.