Hi Precious, you really should not worry about radio signals from IHDs, they are very weak. We are surrounded by radio signals, to name a few; TV and radio broadcasting, wifi routers, mobile phones, doorbells, security systems, remote loudspeakers. The Zigbee 2.4 GHz frequency used by the IHD is not recognised as dangerous. If you turn off the IHD your meters will still try to contact it by sending signals. The IHD itself sends out no data and only needs a brief handshake with the meters in order to recieve data. Of all the devices in homes today an IHD probably has the lowest radio output.
The meters themselves give out a Zigbee signal , and communicate with the supplier by mobile phone connection. You may have become concerned about smart meters through reading American warnings; in their systems they sometimes use high powered radio signals that have been criticised.