Mustard, you have made some articulate and well argued posts for the car - some of which are irrefutable. Thesweetcheat is a bit of a hero in my book, constantly working out his bus and train routes, always willing to enter into good natured dialogue on a subject he clearly feels passionate about. You summed it up, however, with these words "The car is simply too comfortable, cheap and convenient to be easily displaced."
I haven't really got anything to add without the risk of tailing off into gloom and/or grumpiness. For inspiration I recommend Robert MacFarlane's "The Old Ways - a journey on foot" also his "The Wild Places" - reading about ancient routes across and around the British Isles is inspiring and I suspect some (who are fit enough) would be tempted to walk the same 'old ways' at least some of the time.
Which would be a step in the right direction.

Hitchhiking is probably a bit of a taboo activity now but I wonder if it wouldn’t suit some of us. As a student I hitchhiked from Wiltshire to London on a regular basis. Up as far as Durham once, and to Devon and Cornwall every year for several years (where I had a summer job). Never ever had a problem but did meet some generous drivers along the way who’d treat me to a meal or a cup of tea at roadside cafes, or sometimes go out of their way to take me a little closer to my destination. One guy even bought one of my paintings (come to think of it it was the only painting I ever sold :-)

If anyone is tempted to try hitchhiking here are a few tips (if you haven't done it before but apologies if you have). Drivers only have a few seconds to decide whether or not to pick you up (also, whether it’s possible to pick you up). Good drivers hate inconveniencing others behind them so if you’re thumbing a lift choose a spot on a straight bit of road and stand 20-30 yards before a layby, or somewhere else the driver can safely stop. It’s up to you whether you have a sign with your destination written on it (I never did) but if you do use a sign make it simple and clear with PLEASE written on it. Be careful with your bags or rucksack (I once scratched someone’s car with my rucksack frame and felt really bad about it). If you’re worried about your safety don’t get in a car with a driver (or his/her passengers) that you don’t like the look of and (this is something people of my generation didn’t have) once in ask the driver as soon as possible if you can call a friend with your mobile – it’s a clear signal that you’re in touch with the world and they know more-or-less where you are.