If budget is pretty relaxed, go for
smartnav.
I've got it - it's brilliant. Press the button, speak to a human, tell them
exactly where you want to go (business, shop, petrol station, cash machine, anything) and you are on your way. As it's operated by trafficmaster, there is constant monitering of congestion on your route, with automatic guidance around any problem areas.
Expensive outlay and subscription though.