Radiators not heating up but hot water working

[scuzi]

Boiler is producing hot water but radiators are not heating up. Most radiators are on but the main radiator is leaking slightly at the valve - only needs tightened up - would this affect the entire system?

 

[spacethegas]

you have overwhelmed us with the amount of information you have provided us.
have you tried turning it on ?

 

[scuzi]

All radiators are switched on and turned to max., thermostat switched to highest temp and heating and hot water options are both selected. Timer overiden also.

 

[spacethegas]

what sort of boiler ?
what model ?
sealed system ?
are there cold water tanks in loft ?
is there a h/w cylinder ?
what controls are fitted ?
2 or 3 port valves etc ?