Cold with Boiler Running:This could be due to a potentially defective heating pump, or maybe a fault with the pump timer or a thermostat that is incorrectly set. An easy check is to see if the stat is set correctly, then, turn off the power and inspect electrical connections. The lock-shield valve may set wrongly, so you can firstly, open up the manual radiator valve to the limit and remove the plastic dome cap from the lock-shield valve. With an adjustable spanner, open the valve so the radiator can warm up. There are always options like calling a professional plumbing tradesman like an Ashford Plumber who will rectify heating problems. Corrosion in the radiators can be the cause of blockages in radiators. These foreign deposits can block the inlet and outlet pipes. Flush out or replace it if necessary and consider adding corrosion inhibitor to the system.Top Cold:There is a good chance that air is trapped in the radiator. If this the case it will mean that the radiator needs bleeding. Open the bleed valve with a bleed key. This square shaped valve is at the top corner of the radiator. Ashford Plumbers fault find, diagnose and repair equipment.Cold at Middle and Bottom:Again corrosion may be the culprit. This causes a restriction and will not let a good volume flow through the radiator. In this, you need to disconnect and remove the radiator and carry out a full flush. Make sure that you add some corrosion inhibitor to the system when the process is completed.Various Radiators Cold: Visually check the zone valve thermostat/timer is correctly set, reset it if required. If all is set correctly, isolate the power and check the wiring connections in accordance with the original operating manual. The zone valve itself could be faulty, or the system may need to be balanced.One Radiator Cold:This could be due to something simple like the manual valve on the radiator is turned off or maybe the TRVs are incorrectly set or even faulty. If the valve is set correctly but the radiator still does not work, then, it may need to be replaced.