Why is my Central Heating taking so long to heat up?
A very blind shot: Air in the heating system? You have to de-air the central heating radiators, there should be a special vent on it, which might look like this:





You better put some bowl on the floor before you open the vent. If water starts to run out of it immediately, eveything is ok. If not and you hear the sound of leaking air, there's air in the radiator which has to be let out. Be careful, the air is usually quite smelly and water which starts to run out of the vent is usually very dirty and dark at first.