After a bit of experimentation, I settled on the TomTom Go for my needs. It is a superb satnav for live traffic. When Serena suggests a route then you are advised to take it. I have been using it back and forward to Royal Infirmary Edinburgh every day, and she makes subtle changes to the route to avoid traffic. And I know her routes work - as I have disregarded her advice on a couple of occasions. To my detriment.
After the free trial, it is a subscription service, but I am happy to pay £12.99 per year for Serena's advice.