Agree that GPS is not necessary - many of us managed to get from A to B before them! - but nice to have. Great for getting you out of a town or city as much as anything else.

Bear in mind that when you download Google Maps offline, it doesn't always have the ability to calculate a route offline; just display the maps. (Unless things have changed recently.) Other apps, e.g. Nav Free, do. Don't expect much phone signal anywhere in the highlands.

Also, you should know there are stiff new penalties for using your phone in a car in the UK. You should make sure it's properly mounted (you can get a windscreen suction mount in most petrol stations) and preferably avoid touching the phone to enter an address while you're driving.