I wouldn't go near anything that combines a "wax" and an automatic car wash.. If you put a good layer of a top sealant on before the winter, you should never need to add a "wax" to the car. I put three coats of Zanio on the car in October as soon as I got it, and water still is beading like crazy almost 4 months latter.
If the "undercarriage" you talk about is just a wash... that's not a bad idea in the winter with all of the salt around... if is some "undercarriage sealant" that's not going to be worth it...
E46 325xi Oxford Green/Sand Leatherette/Myrtle Wood Auto ZCW - Retired
E90 330xi Mystic Blue/Black Leather/Aluminum 6sp Manual ZSP/ZPP/ZCW/CA - Retired
F22 M235i Mineral Gray/Red Leather/Aluminum 6sp Manual ZPP/ZTP