Know Your Stopcocks

There should be a stopcock on the mains feed into your house. This is often under the kitchen sink. Make sure it works!

You and anyone else living in your house should know where this stopcock is and how to turn it off!

Somewhere outside your house there will also be a mains stopcock. This will almost certainly be below a small trap-hatch somewhere on the street or road outside. However, if a new drive surface or road has been laid, the hatch may become concealed. Make sure you know where it is, how to get to it and that you can operate it.

You should also know where the hot and cold down service valves are. They are usually in the airing cupboard or loft. Make sure they work.
If you are unsure of the whereabouts of any of these valves or stopcocks, ask your plumber next time he visits. He'll be more than happy to advise.

Burst Pipes

The first thing to do with burst pipes is turn off the mains stopcock. This will stop any more water coming into the house, and reduce the pressure of the leak. However, if the loft storage tank is full then there could still be quite a lot more water to flow out, so opening all other taps will probably help in reducing the amount coming from the leak. Get buckets etc to catch any remaining water coming out, and then deal with any flood water and damage. If there is any significant damage to furnishings, it's worth taking pictures for insurance purposes!

Cutting out the burst section and fitting a new section of pipe yourself is not really feasible for anyone other than the very competent DIY enthusiast who understands plumbing joints etc. So this will be a job for the plumber.
Hopefully the pipe will be visible, or simply behind a kitchen unit or in the loft where it is still reasonably accessible. In which case the plumber will be able to cut in a new length of pipe quickly and efficiently - they've done it thousands of times before! Clear everything away before they arrive and make as much room as possible for them to operate in.

Gas Emergency

What's the first thing you should do if you smell gas?

Do
Open windows and doors to get rid of the gas.
Check to see if the gas has been left on, or if a pilot light has gone out. If so, turn the appliance off. If not, there could be a gas escape.
Turn the main gas tap to the "OFF" position. The supply is "OFF" when the ridged line on the spindle is across the pipe.

Don't
Turn any electrical switches (including doorbells) on and off. You can, however, use the telephone to call the emergency number.
Smoke
Use matches or naked flames.
Leave it to someone else to call - you could be putting yourself or others at risk.
Use a mobile phone if in the vicinity of a gas leak.

Telephone immediately
Natural Gas - Phone Transco's emergency number Freephone: 0800 111 999 immediately, It's open 24 hours a day 365 days a year.
Calor LPG gas bulk tanks - Phone 0845 7444999, It's open 24 hours a day 365 days a year.