Well done on losing over 3 stone - amazing! Weightwatchers say there's no such thing s 'naughty' foods as you can eat anything you want as long as it's in moderation! I don't think I ever go a day without chocolate in some form or other.
I personally wouldn't try to 'lose' weight over Xmas as there's too much tempting stuff around. Perhaps carry on trying until Xmas/New Year week and then just try & maintain rather than put on. I don't know whetehr that's a negative thing to say but to me just staying still and not gaining would be a struggle over Christmas! Try to buy 'lower' versions of foods and don't buy as many Xmas Nibbles. Just 'cos the supermarkets are selling Buy '1 Giant Tin of Nuts/Chocs and Get 2 Free' - it doesn't mean you have to buy them. That's what I keep telling myself anyway!
Good luck and speak to your GP about the smoking thing as loads of GP practices have someone there who helps people give up smoking and has tips/ideas etc. We have a nurse at ours who does it.