Vintage Air is a great company to deal with. I have a vintage air condenser in my Exige
I would suggest starting with the factory parts, they are usually available from race car guys.
With proper mods the stock system works reasonably, heat is powerful AC less so.
The problem with installing one of their mini kits is the odd way the Exige system is set up. The air all goes through the 3 1/2 inch tube to a separate diverter assembly. This assembly is, I think, the weak point. Airflow out of the heater box is pretty significant, but seems to get lost in the diverter.
The Vintage mini assembly is pretty nice, i have the earlier version in my +2[but have not used the AC as of yet]
I think to install the Vintage unit you would have to make the recirc vents mostly heat out vents, run individual hoses to the face vents and defrost vents, and also since from the factory the heater is actually outside the car, make a cover similar to what I did:
note that my efforts were merely icing on the cake to the efforts of others who did the work of figuring out how to make the heat/ac work much better.
I think my post are a pretty good integration of several previous efforts, with a few new mods.
Also, I believe the Vintage controls will work with the factory controls, the 'old air products' valve I used does.