iphone based nav- suggestions please

[glasgowrob]

looking for a decent nav app for iPhone, ideally something that will still work without a 3g signal,

not fussed if its a paid for or free app as long as it can be used anywhere in the country without the worry of getting a decent reception first

[glasgowrob]

how do you find it in areas with poor or no reception?

[glasgowrob]

bought the 3d version of copilot and picked up a tomtom start 25 as a backup just in case