We disconnect any existing thermostats. Then we can either leave them in place or take them out.
If we take them out, we can fix a blank plate over the hole they leave but you will be responsible for any decorating to make this good.
If we are installing a new Nest Learning Thermostat (smart thermostat) in place of the existing thermostat, then we install it as neatly as possible. However, you will be responsible for any redecorating around the new thermostat.