do I have a fult in the system.... and if so any idea what the fault
maybe??

That depends on how the system is designed to work. We need to know the type
of control system fitted. Do you have zone valves? If so, how many and what
type? Do you have TRVs on all radiators? Do you have a room thermostat?.
What is the cylinder thermostat set to? Does it click when you move it up
and down?

Christian.