I have a Glowworn Majorca fire/back boiler. Some of the upstairs radiators get warm but not hot when the heating is on. I have bled them numerous times (with the heating turned off) and released air but they never get as hot as the downstairs radiators. Im not sure what kind of heating system I have or if there is a cistern tank somewhere that needs topping up (its not in the loft) could it be the pump thats not working? Any advice would be very welcome.