Originally Posted by Stuart C

Dunno if it's still true, but one thing that you used to need to look out for in VOIP providers is that they (particularly Skype and Vonage) frequently blocked calls to 999.

Also, there's the practical aspect of what you do if there is a fire, or powercut? In either case, your router and/or modem will probably not get power, so will not handle outside calls. Phone lines are powered independantly, and are legally required to have battery back up in the event of an area power failure.

Of course, if you have a mobile with some power and a signal, this is all covered.