Thanks.  Interesting episode.
A few things did occur to me while listening.  As I think I said, I’m not an English guy: my background is in the sciences, so these are strictly amateur thoughts, but might be worth throwing in.
First: on the classical material.  I immediately thought of Lucan.  (I’m actually more familiar with the rather funnier Lucian! But never mind.)  The witch in Pharsalia — her name escapes me right now — is a horrific figure.  C. S. Lewis has some interesting comments on this in “Poetry and Prose in the 16th century”:
http://www.amazon.com/Sixteenth-Century-History-English-Literature/dp/0198122314/
I just looked at the book, but can’t find the relevant passage, and the index is no help.  Basically, she does filthy things.  Lewis, as I recall, says *the* question is whether anyone ever did such things or whether it was all coming out of Lucan’s imagination.  And since later ages probably took Lucan as a true account … well, you’d get inquisitors asking suspects whether they’d done the things they (the inquisitors) had read about in Lucan, and, under torture, they’d probably say they had.  So witchcraft scares may have been partially driven by literary imaginings.
(Lewis is also interesting in this same book on the renaissance interest in both magic and science (comes up also in “The Abolition of Man”).  He says something like they were twins: the one that was found to work survived.  (This is the point Michal made later in the podcast.) )
Here we are: I just googled up a text of Pharsalia:
“Haggard and loathly with age is the face of the witch ; her awful countenance,
overcast with a hellish pallor and weighed down by
uncombed locks …”
There we have the “hag-like” image of the witch one of you referred to.
Whether or not anyone in mediaeval and renaissance Europe was trying to do anything really sinister I suspect most “witches” were just harmless people who had a few simples and few memorized charms.  I’d think in a Christian society many of the charms probably had a Christian form — they’d incorporate saints’ names and suchlike — but from the viewpoint of Christian theology would reflect an unacceptably magical view of things — since the efficacy would be seen as residing in procedures or incantations or objects.  Keith Thomas mentions practices of this sort in his famous “Religion and the Decline of Magic”.
http://www.amazon.com/Religion-Decline-Magic-Penguin-History/dp/0140137440/
IIRC, people would do things like save communion wafers and put them in the furrows of ploughed fields in the hope of inducing fertility.  I guess there’s a sense in which this is ostensibly Christian but actually in effect betrays magical thinking — since it assumes that the host will “work” for one’s own purposes, efficacy residing in it as an object, rather than its efficacy being according to God’s pleasure and happening when taken sincerely and used as His son directed.  (C.f. interesting to see “magical” uses of the host coming up much later in the novel “Dracula” — as a door sealer!!)
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Secondly: Alan Macfarlane of King’s College Cambridge:
http://www.alanmacfarlane.com
is interesting on English witchcraft beliefs in “The Culture of Capitalism”.  This is an old book from the 1980s.  Macfarlane is an historian as well as a sociologist.  AFAIK, at the time he learnt it sociology was assuming a late emergence of “individualism” across Europe in line with what people like Marx and Weber had asserted (assumed?).  Macfarlane actually found when looking at the historical evidence that “individualism” had emerged much earlier in England and that England had never really had full “feudalism” in the sense in political scientists use the word.  Among many other things, he found that witchcraft beliefs in England were quite different from those in much of the rest of Europe — even Scotland.  So it wasn’t generally believed that gangs of witches met for “witches sabbaths”.  In England the witch was conceived as a lone figure — almost an “English eccentric” only rather more dangerous.  This was probably a reflection of the fact that English society was more individualistic.  The Continental  witchcraft beliefs were a reflection of a more communitarian society — its imagined inversion.
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Thirdly: on the Salem witch trials.  There’s an American historian — I forget her name — who has advanced the intriguing theory that what was going on there was ergotamine poisoning.  As you probably know, when the ergot fungus attacks rye, a substance similar to LSD is produced.  Now rye was not a common crop in England, but some was grown in East Anglia, which was where many of the people in the newEngland settlements came from.  This lady says that the years in which the witch scares happened were unusually wet years.  This would have encouraged the ergot fungus.  If someone ate bread made from ergot-tainted rye flour they would experience some very strange symptoms that they might well conclude meant they had been bewitched.  Alternatively, they might start behaving in strange ways that would lead others to think that they were a witch.  There also seems to have been a rather unfortunate witchcraft test in use at the time.  What people would do is bake a “witch cake” and throw it to a dog.  They’d marked it with a suspect’s name; or perhaps they just said the name; I can’t remember which.  Anyway, the subsequent behaviour of the dog was taken as a test.  I think you can see that if that cake had been made from infected rye, the dog would, indeed, behave pretty strangely, and perhaps die.
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Finally, on New Testament references.  You guys are far better at this than me, but as it happens I just re-read Acts. there’s another in that book: Simon Magus.  I just checked the reference: it’s chapter 8:
“But there was a certain man, called Simon, which beforetime in the same city used sorcery, and bewitched the people of Samaria, giving out that himself was some great one …”
I recall that Bede, who knew what result he wanted at the Synod of Whitby was who very rude about Celtic Christianity, said that the Celtic tonsure was the haircut of Simon Magus and therefore evil and heretical!