Hmmm... while nobody would argue that smoking is healthy or a good idea, I very much doubt it plays a big role in PN - apart from hindering B12 methylation (which can be mostly corrected with supplements) in the short term.

I think when you are just coming to terms with a pretty horrible illness, the last thing you need is people telling you you are in denial. No offense, but I don't think that's very helpful right now.

Yes, the mid to longer term plan should be to quit. Obvious. But. One of the side effects of quitting is anxiety attacks (been there...), which can be unhealthier in the short term. So one might want to take their time to take stock and see what can be changed when it comes to lifestyle.

I'm still dragging (pun not intended) my feet about quitting, not so much because it affects my PN - it doesn't - but because it's horrible and expensive.

So yes, do plan to give up, but perhaps wait until you are in a better head space. Your GP may be right for now - they sometimes are.