[jambo]

112 works on any GSM network that your phone supports. It will use say an O2 transmitter even if you're with Vodafone. If there are no GSM posts near you then you're out of luck. People sometimes get a bit carried away and claim it works on the underground and uses satalites and would work where a normal mobile wouldn't, which is rubbish.

As far as I know 112 is simply used to provide a standard, on my phone for instance 911, and 999 also get through the key lock and should work in the same way as above.