Had a 330 E46 and asked the dealer how much to add sat-nav. The estimate was around 3k. Looks nice in the dash but if it is anything like the system in my 335i a Tom-Tom blows it into the weeds.
Definitely not worth the expense. A TomTom or similar is streets ahead (geddit?) and at £100 vs £3k is such blindingly good value as to make a retrofit seem pointless.
I'd hazard a guess that your car will not be worth £3k more at resale with it fitted, either.
