morddwyd, I do not have a smartphone myself but my daughter does and says that using the satnav is very expensive.""
I expect she is using the data services which obviously incurs continuous charges.
If she wants to look at other options in addition to Tom Tom I have used Co-Pilot, Route 66, N avigon (Garmin) and Sygic, which uses TomTom maps.
All are free to use, but have to be bought initially.
As has been said, TomTom is good, and so is Sygic.
I think most have a free trial option.
Advantage of a smartphone version is I can use it on my mobility scooter. I carry one in the car and the satnav can be useful shopping in Edinburgh or Glasgow!