Also this year do a favor to yourself and your children: make sure your Christmas three does not end up in the garbage but it's recycled via proper facilities.http://www.itv.com/news/london/2014-01-06/how-to-recycle-christmas-trees-in-each-london-borough/
I have included a link for London neighborhoods a bit outdated but imho still helpful. People from other cities might want to contact their local council for more information.
We breath 7-8 trees per year per person. Considering there are about 60+ millions people in U.K., it would be helpful to have some Christmas tree back to life.
A human breathes about 9.5 tonnes of air in a year, but oxygen only makes up about 23 percent of that air, by mass, and we only extract a little over a third of the oxygen from each breath. That works out to a total of about 740kg of oxygen per year. Which is, very roughly, seven or eight trees’ worth.