It looks like you have a Honeywell R6660D Receiver, and Wireless Battery Operated Thermostat. The wires are connected to the Receiver and the Thermostat communicates with it wirelessly telling it to turn the heating 'on' or 'off' as required.
If you want to leave the existing 'iflo' timeswitch (actually a rebadged Drayton) in place and just replace the thermostat and receiver you can do. If you go down that route you can buy a new wireless receiver and thermostat and simply replace the those you have. Or...
...Buy a simple wired thermostat which will replace the existing receiver and thermostat, but you may have to run a new cable from the receiver to the location of the thermostat. Or...
...do as
@Alec_t suggests and replace the 'iflo' timeswitch and existing thermostat with a programmable thermostat that contains both functions in the one device.
For DIY a new new wireless receiver and thermostat would probably the easiest option wiring wise. Although from your photo of the R6660D receiver it appears some wires have been removed from A & B, I assume this is to get the heating working without the thermostat, you will have to reinstate them.