heating only switching on in part of the house

Hello all
Hope somebody can help!! We've got a Gledhill SP A Class Boiler mate; and an Ideal HE12 boiler. We have two thermostats in the house, one on the 2nd floor (controlling heating on the 1st and 2nd floor) and one on the ground floor. Our issue is that our heating on the 1st and 2nd floor seems to work perfectly fine, i.e. the heating switches on and switches off in line with the temperature setting on the thermostat control. However, the heating on the ground floor is not switching on at all. Our hot water is working ok.
Can anyone advise what the issue may be?

Thanks in advance!!

Well it sounds to me your heating is zoned.
There may be some motorised valves controlling these zones via the room stats.
It would help if you said where in the UK you are.
Then someone may help you further as they may be aware of your "local" problem.
I cover Norfolk and have not come across any units being zoned yet
Mike
MGC/H2O
Norfolk

Thanks Mike. We live in Medway/Kent.