HI,
I also have a 2011 3.0l XF-S, had it for three years come October. So have been through 2 winters with it.
Living in West Sussex, I don't often get to see really bad snow or ice (but when it does come, the response is ill-equipped to deal with it!)
Being retired, I don't have to go out in the occasional ice & snow, but I have given it a go a few times using the winter mode setting for the traction control. That seems to work fine with normal tyres (Pirelli P-Zero 255/35x20).
I guess if you need the extra security, winter tyres would be a good move, but I can't justify them for 2 or 3 weeks a year.
Enjoy your XF!
J