Hey there Fiatboy,
The header tank is situated on the left hand rear quarter pillar of the tailgate shut, as for the heater controls they should be fairly well infront of you, there are two possible reasons why your not getting warm air.
Firstly check your coolant level and make sure you have the corect amount
1. heater matrix is blocked or bypassed.
Easy to check, look underneath the dash where the center console comes to an end, you should be able to see if the matrix is still connected.
If it is with the engine runing feel the piped to see if they get warm.
2. Thermostat has been removed or water/coolant level is very low.
The Lancia has a major flaw with its thermostat location ie bottom hose, this is the last place for a thermostat to work properly hence so many head gaskets go west!
Again with the engine running but AVOIDING the cooling fan feel the water hoses to make sure there is a satisfactory rise in temperature.
With regards your laws, your bound to get locked up and the key's thrown away

(ONLY JOKING)