How to bleed your radiator.

If your radiators are not heating up properly or they have cold spots, they might just need bleeding:

Radiators need bleeding when air is trapped inside them which stops the water circulating around your radiator.
If your radiators are noisy, making a gurgling or banging noise, they might need bleeding too.

What you will need:

Turn on the central heating to allow pressure to build up in the system
Identify which radiators need bleeding by feeling for cold spots or listen for a gurgling sound. Take care when touching the radiator as they will be hot.
Switch off the heating and wait for the radiators to cool down.
Prepare the area by placing old towels underneath the radiator to protect the flooring.
Insert the bleed/ radiator key into the bleed valve. Turn the valve slowly anticlockwise. You should head a hissing sound which is the trapped air coming out. Use your cloth to catch any water that comes out.
Retighten the valve when the hissing stops and liquid is coming out.
Check the pressure of your heating system by looking at the gauge on your boiler. Bleeding radiators can cause the pressure to drop. Top up the pressure if necessary.
Check to see if your radiator(s) are heating up properly, by feeling to see if the heat is spreading evenly throughout the radiator.