Scotland (if I have to pick a city, Edinburgh). I don't really know what the job market is there for software development though. NY is great because of the huge market, but after traveling all over the UK (and Scotland twice), both my wife and I would love to live there. There's not nearly as many people as there are here in the US (which is a plus), and it's beautiful everywhere.
It's one of the few cities in the UK that I would be tempted to move to from Bristol.