Cheers guys, I have an old iPhone 3GS somewhere but I guess that would be pretty slow and rubbish so I'll just use my Nexus 5.
I assume it's just THIS app (lots of reviews saying you now need to use data to open the app though)?
I'm with Orange, had considered getting a 3 PAYG SIM but no real need.
Yeah dont use an iphone3, tomtom runs like a dog on that thing and the handset also has a weak GPS chip which struggles in the highrise areas in the states causing much frustration when "downtown" in any city there. (i know this from experience!).
I changed out for an IP4 and its miles better, the GPS chip is much stronger and the phone is much faster.
As Fox mentions, its nice to use a dedicated device, a Jailbroken IP4 with retina display and tomtom loaded (i have the whole developed world on there!) makes a fantastic international satnav and leaves your actual phone free.