As said, get Nav if you think you need it AND will use it a lot. I didn’t bother spec’ing it when I bought my car as I don’t use Nav that much. Take this scenario ….. so if I had the need to use Nav for about 20 times in the time I own the car then for a £2K Nav system thats £100 for each time you use it!!!!!
You could buy a TomTom for just one of the £100’s.
If you spec Nav then you would get some money back when you come to sell it - but not much.