Unfortunately the Williams etc paper showed that the proponents of glaciation have ignored or were unaware of the examples of effort /ingenuity in Britain

Indeed. Of which there have been a whole series stretching over many decades. I wonder if the fact many of them were amateur efforts and therefore didn't make it into "the literature" has something to do with it?

On the other hand quite a gaggle of well known archaeologists were at Foamhenge and some even had a go with both the oars and ropes so maybe the climate will change as a result. Mike Pitts has already mentioned rowing as a possibility.

Like you say, the jury's quite rightly out on the issue and saying one explanation is more likely by default because the other is unlikely isn't on. It's got to be 50-50 I'd have thought.