Nintendo and O2 have partnered to provide 3DS owners with free access to O2′s wifi network across the UK. You'll be able to access online services at thousands of public venues, including McDonalds, Pizza Hut and Toby Carvery, assuming you don't mind getting a bit of grease all over your Animal Crossing machine.
There are also hotspots in Debenhams, Costa Coffee and House of Fraser, as well as The O2 (naturally), Twickenham, Bluewater and the across the entire London boroughs of Westminster and Kensington & Chelsea.
As long as you have the latest system update, you should be able to get online at any O2 hotspot with minimal fuss. It'll even download software updates while you're in standby, as it would at home. Already this sounds better than EE's WiFi on the Tube thing where I have to view a Virgin Media splash screen in my browser before refreshing Twitter during the 15 seconds I'm at a station. Urgh.
The Nintendo/O2 partnership is already live in certain, unspecified areas with more coming over the next few week. You should be able to find locations on theNintendo Hotspot FinderTwitter competition from O2.