Hey Ross
I have read (but can't find the reference) the following tid bits that might interest you.

Smoking is implicated in approx 80% of either head and neck or oral cancers (can't remember which)in countries like Australia, NZ or the US
Drinking AND smoking multiplies the chances of developing oral cancer
Drinking alone has not been definitively linked with oral cancer
Smoking during radiation therapy lessens the beneficial effect of radiation and impacts negatively on survival

So whilst it is likely your cancer is smoking related, it is a good thing you gave up when you did as you have improved your chances of survival even at such a late stage. The reference for smoking and radiation comes from the New England Journal of Medicine by Browman et al way back in 1993. There was also something that was reported in the Science magazines this year that said a similar thing but I have been unable to access the actual trial to check it is solid.

Maybe the reason there are less smokers than you would think on this site is that most who survive to post here have given up, and the ones who haven't given up aren't here. Also consider that older people don't "do the net" which gives us an atypical young group who may also be more afflicted with HPV related cancer. Plus, some of us (me and Alex) just don't put it in our profile because it is embarrassing, or ancient history or just assumed.

Karen