Depends where you are travelling, I think. My Garmin has stood me in good stead in many a barren, featureless waste, although Lisburn looks like that on most days. I've become strangely attached to it, and always carry a couple of spare batteries for when the car's cigar lighter packs up. If you only want to navigate Manchester's streets I'm sure there are cute packages available for those little hand-held computer thingies, but so long as they can tell you where your vital destination is you've got it cracked.
Oddly, among my 'saved' routes, there's one describing a couple of hundred miles at 5000ft above the middle of the southern Indian ocean, E to W. My memory must be going.
I use the Navman Pin 168 pocket PC,bought through http://www.globalpositioningsystems.co.uk the SmartST Navagation system that came with it is spot on for navagating round the U.k roads.Plus the Navman I use is compatable with Memory Map- www.memory-map.co.uk so I can use ordnance survey maps by putting in a new memory card similar to those used by digital cameras.This I use for cross country work on the moors/hills near where I live and gives me a 10figure grid/altitude/speed read out,main programme goes on my home PC and I can plot routes,times and distances plus look at route in 3D walk through mode as well then download onto Navman,a facility not available on many handheld gps.Its a system that suits me fine for both types of navagation but visit 'globals' website and have a browse as they also do some cracking accessories as well.