he says the transportation of the bluestones requires a great deal of imagination

Well, a great deal of experimental archaeology perhaps - e.g.

"stirring tales of primitive men hauling massive bluestones on sledges"
- but evidence suggests they did it with Sarsens from Avebury

"has anyone seen the tidal reach up the estuary"
... but estuary-going Bronze Age boats have been found e.g. at Feriby.

"the assumption that a) Preseli area was a sanctified area, b) that they desired/sanctified the stone type which was used for stone axes. Lot of non-rational thought there then..."
But a rational assumption that they brought their pre-existing circle with them answers that at a stroke.

I think he's glacier-biassed (just as we're human-transportation biassed) and he's quite wrong to say human transportation is a fanciful idea.