Indeed, and I'm afraid the OP was wrong, certainly for BE. "Satellite navigation" is uncountable, but that's only one of the meanings of the noun "satnav", as ewie pointed out.The OP said that it is uncountable.
We have exactly the same usage in BE, and the same countable non-countable usages as for satnav.As you probably have realized, in the US you say "GPS" and that is countable. My wife and I have two GPSes, one for each car.
satnavGPS to find my way - I used a system of satellites and an associated receiving and computing device to find my way.
I used a
satnavGPS to find my way - I used a box with Tom Tom (or Garmin, or Mio or ...) written on it to find my way - I don't care how it works.
As I said before, both terms are used in BE. If you go into your local car accessory shop in the UK and ask for a GPS you will be pointed to the in-car satellite navigation systems without the least indication of surprise from the shop assistant.I'm looking for a satnav - in the UK / I'm looking for a GPS - in the USA. In both cases meaning the gadget itself.
Well, then, you had better get married.Maybe: I'm looking for a navigator (for my car) in both the UK and the US.