I ended up spending it alone last year and it was horrible.
But it doesn't have to be. Personally I don't celebrate it, and that's fine for me. If you are going to do Christmas for one start planning for it, and make it special for you. For many years my grandmother spent Christmas alone, through choice.
Start the day with a bath and a 2 glass mini bottle of champagne.
Have a nice breakfast, or don't, or have chocolate.
Put on your favorite music, put on a new dress and dance.
Make something special for your dinner, no scratch that, have what ever is your favorite, whether that is salmon or shepherd's pie.
Watch exactly what you want on TV - it doesn't have to be the corny Xmas stuff. A couple of years ago a friend and I watched several hours of 'extreme make over - home edition' - we both ended up bawlling. So don't watch that, unless you want a good cry.
The fact is, the hapy family all comming together and enjoying Christmas is not reallity for many people. You cannot change your family.
Alternatively you could volunteer for something like crisis, or ask if your hospital needs volunteers. How would you feel about having a couple of pensioners for Chritmas lunch? Or volunteering at one of the council run christmas lunch events.
www.crisis.org.uk/pages/volunteering-at-crisis-christmas-2009.html