Your post says a lot, Rowland, and there are many points to note, but mainly, the towns' centres will dry up if they keep up with excessive parking costs, and charging high rates for shops. I really can see that the old 'High Streets' won't be around for many more years, and we'll all be either shopping out of town, or online!
Although we're supposed to be a big village here, (Tunbridge Wells once tried to 'class' us as a town, until we all told them all to get stuffed), and we have two small supermarkets at either end of the spectrum, i.e. Waitrose and Tesco. Both are fabulous places and we regularly use both for different reasons. Why I'm mentioning this is, as long ago as the early eighties, my company was heavily involved in developing and building the 'new' out-of-town shops. One of the ideas was that a smaller shop (like we have), would cater for all the villages within a certain radius, and Budgen were the first to understand this!
Budgen did indeed become the first to come here, several years ago, but they didn't seem to fit in well for some reason, their marketing was abysmal and they tried franchising with a local firm, Jempsons, which is a fabulous independent around here. That didn't work, so the site eventually went to Waitrose (although the site freehold is owned by Sainsbury's - work that one out!), and when Tesco came in over the road, the idyll was complete!
The upshot is that we never even go to Tunbridge Wells nowadays, except for the out of town BandQ, Currys etc, and we really don't want to park for too much dosh and trawl the place ever again!