1. Having only got around to this after a busy weekend, I have tuned in to this highly entertaining thread. The consensus seems to be that this was an excellent puzzle. I agree. For an extra frisson, I suggest using coloured pens to demonstrate the effect.
2. Those of us who prefer to sip the Listener puzzle, like a good wine, may have had an advantage this time over those who like to gulp it down. As others have observed, those who thought thay had solved the perimeter quickly may have done themselves a disservice.
3. It is true, as S-Martix points out, that the puzzle was [probably] easier to construct than to deconstruct, but that is irrelevant. I could easily create an unsolvable puzzle, or conversely spend weeks constructing one that everyone could solve quickly. There are no correlations among constructability, solvability, and admirability. Picasso once created a bull's head by welding together a bicycle saddle and a set of handlebars; it probably took him about five minutes, but the result was and remains a stunning work of art. Whistler, during his court action against Ruskin, said that he didn't charge for the amount of time it took him to create his painting "Nocturne in Black and Gold: The Falling Rocket" (about half a day), but "for the experience of a lifetime". Kea's effort is not a Picasso or a Whistler among crosswords, perhaps, but it was very good nevertheless--perhaps a John Singer Sargent or a Samuel Palmer? :>)
4. However, before assuming that the grid was so easy to construct, one should perhaps try it oneself. I challenge S-Matrix and other antis to have a go, using the phrase "round about thy table" (Book of Common Prayer) (12 x 8).
5. I have two minor criticisms of the puzzle: (a) that the symmetry was only one-way, rather than two-way (room for improvement there in the challenge); (b) that the clues were presented out of order.