If you own the property, it is likely that the thermostat, radiators, taps, underfloor heating equipment etc. will be your responsibility to maintain, but it is worth checking your lease agreement.
The Heat Interface Unit (HIU) and heat meter do form part of the primary heat network, so may be the Building Owner/Freeholder’s responsibility, however this would also be stipulated within the lease agreement. If you are a tenant, please contact your Landlord or Letting Agent to find out more.