Wireless setup

Hi,

I've just had a new Viessmann combi boiler installed today and I was under the impression the tado thermostat would be able to wirelessly sit with me in the room I'm sitting in around the house. However my plumber has installed it in the airing cupboard in which the boiler is located. This is pointless right? I have read that I need the extender and that should have been in the airing cupboard by the boiler and the thermostat then can be anywhere? Doesn't need to be mounted? Is this correct? If I was to get the extender would it plug onto the mounting plate of the thermostat already wired or will a new mounting plate need wiring?

Thanks in advance for your help.