I was fortunate enough to have done ss between Feb and July, so didn't have a Christmas to contend with! However, for four/five months prior to Cambridge, I was on Atkins. I surprised myself by sticking to it over Christmas - I ate whatever I liked, so long as it was low carb! I had the meat and veg for dinner, and made a lovely sausagemeat stuffing (so good, that my kids and fella now ask me to make it again every year!). I had berries and cream for dessert, and just a couple of glasses of wine, and a few other low-carb drinks over the period. I managed to avoid the choccies, but did indulge in just a few low-carb goodies i'd bought myself, and some nuts. I can't say I wasn't tempted by the roasties (they're my fave thing on a roast dinner!), but I didn't die or anything by not having them, and still thoroughly enjoyed my Christmas dinner.
I think if you're planning to eat over Christmas, low-carb is definitely the way to go, as you can still enjoy the food, but won't find it difficult to get back on to ss. I didn't lose any weight during my 'Atkins Christmas', but I didn't gain any either, which was a first for me!
Jo x