Gas boiler problems
This weather isn't the time for your gas boiler to pack up but if it does, here's a useful tip...
Modern condensing boilers have a condensing pipe, usually white plastic or copper that leads to a drain, often outside. If this pipe freezes up in the cold weather then it will cut the boiler out as a safety feature. This is quite a common occurance in winter so if your boiler does cut out and you don't know why, then the first thing I would do is to locate the condensing pipe and pour warm water over it to free up and ice which may have formed a blockage then try to restart the boiler.
A simple job which can save both the wait for and the expense of an engineers call out in many instances.
Of course it may not have been that, but it costs nothing to check this first just in case.....