Ok, I will vote against Garmin.
Functionally, it's fine, but is clearly American, designed for American roads. They have very different road systems to us!
For example. You'll be on a roundabout, and it will say "take the 3rd exit onto William Brown way". When everyone else, including the signposts, would call that the A621! Ok, not a problem if it's a 4 exit roundabout, but if it's a 5+ exit, it's a nightmare. You can't use the signposts, you end up squinting at a possibly non-existent road sign (usually just as you pass it)
I was all set to get a TomTom to replace our satnav, but actually we just ended up using our phones - if you have fairly decent phones, I'd recommend this, just download an app.
I've heard Co-pilot is good, I just use google maps (iPhone), not sure what app DH uses for his windows phone, but I can find out if you like :)