Radiators
Whatever style you choose radiators all essentially work by heating the air that surrounds them via radiation andor convection http://www.simplifydiy.com/plumbing-and-heating/radiators
Bleeding a Radiator
Air can enter your central heating system whilst the water level in it is being topped up http://www.simplifydiy.com/plumbing-and-heating/radiators/bleeding
Radiator Thermostats & Valves
There is little to choose between the two methods so personal preference should decide which best suits your heating system and room or house http://www.simplifydiy.com/plumbing-and-heating/radiators/thermostats-and-valves