Very interesting post Tony, and I think it could be the start of a heated (sorry, bad pun) debate.
My opinion is that I am not overly concerned about the impact of my 8 on the overall environment because:
1) I will not use it every day
2) it will be well maintained and thus it's emissions will be within tolerances (compare with a newer but badly maintained car)
3) The replacement argument is for me BS - I used to drive a 40 year old Sunbeam and had to field questions from greens about its emmissions etc - the argument that normally gets overlooked is the cost and environmental impact of the energy needed and the raw materials required to build a new car. An existing car, even if heavily driven will still not produce as much impact during its entire lifetime as the impact of building a new car.
Being in Switzerland I couldn't see the CH4 programme but it sounds very interesting - what's the basis of the argument? (In contrast to the UK we got "The Day after Tomorrow" to view yesterday, I'm beginning to wonder about the possibility of a conspiracy going on with the Global Warming Topic
Having said all that, I do recycle bottles and paper but that's simply because it's convenient to do so and I don't see the point in wasting raw materials