The bad news, though, is that patio heaters aren't energy efficient, and contribute to global warming.....

You're right - I believe these are particularly bad for the environment and should be banned, IMO :-)

According to an article on the BBC website, a patio heater emits as much CO2 in 2 hours as a car would emit all day (see here).

I wonder what effect all the smokers are having on the environment, and what benefit it would have if they were all to give up? Are there any figures?

The main problems with introducing the smoking ban are

(a) that it affects people other than the person doing it, a message which seems difficult to get across to smokers, who often compare it to drinking, breastfeeding and other things; and

(b) the status quo is always difficult to change - it's always more difficult to remove a privilege than introduce it. I would call smoking in pubs a privilege that is about to be withdrawn, rather than a "right".