colinjones,
there is a wiki entry on the provider 1und1, which details what needs to be setup, if you have your core not connected with a public IP address.
re Z-Wave thermostats: Tschak, the Z-Wave thermostats only do setbacks, and not full control of the heating. IMHO, a setback of 4 degrees celsius should be enough, but thatcrazyperson123 explicitly stated he does not want it.
rgds
Oliver