Do you have pics of the entire process? It would be a priceless contribution for those who would try this assembly, I'd like to see the heater/cooler unit in pics. Can the 131 A/C play as an heat pump also?
Normally on European cars, it requires complete dash removal to install AC, different from Japenese were the evap. was slided in underneath the glove box and everthing else (recirc. and wiringloom) was pre-installed
In General we would quote for 2 days labor for a complete install as most European cars were not prepared for AC
A heat pump would make sense if there is no heater but performance and efficientcy is poor (Only for not too cold countries)
Basically an AC system pumps heat from the interior to the outside by absorbing heat in the underdash evaporator and reject it by condensing it at the condenser (in front of radiator) In the reverse mode (by means of a 3-way valve) the evaporator becomes condenser (Rejecting heat) and the condenser becomes evap.(Absorbing heat) In this mode it is absorbing heat from the outside and "pumps" it into the interior.
It is instant heat (direct available) but you can imagine that there is not much heat to absorb from the outside when it is freezing outside.. basically your are pumping the compressor energy (=heat) inside.
Heat pump mode is not realy used in the automotive industry but is getting a topic now with Hybrid cars and efficient diesel engines were there is less waste "coolant heat"
Toyota uses a "hot Gas" systems (heat pump similar system) on some diesel engines as a "cheap auxillary heater"
If there is interest for a more detailed explaniation (physics etc.) let me know.
Cheers
Henk