Just as a side point. When they said that the heater wasn't working in your section I believe they were not being entirely truthful. What they should have said is that the air conditioners are working too well.

Fresh air enters an airplane through the engines. That air is pressurized and very hot. It then goes through the cooling packs (air conditioners) to cool the air to a comfortable cabin temp. Normally you will see more complaints about it being too warm on the plane since some airlines will try to save money by shutting down some of the cooling packs during the flight (which saves fuel).

Here's a quick synopsis of how it works:

http://www.boeing.com/commercial/cabinair/index.html