That’s what I was asking Avocardos is it not something those people saying they don’t need a car in London want to do.
Me and my group of friends go camping, hiking, mountain biking, rock climbing quite a lot so getting out and about is a big thing. Without a car it’s much more difficult and so I guess that plays a big part.
Camping in my mind is a one a year holiday sort of thing. I haven't felt the desire to go since I was a child (it tends to be more backpackers hostels in developing nations nowadays) but if I wanted to go to Devon for the week or something I'd hire a car - there are lots of car clubs.
Hiking - depends on the distances - I think most people are happy with parks and so on, but if not I'd get a train out of London and start hiking from the train station.
Mountain biking - lots and lots of cycling in London. Much of it is road / commuter cycling, but there's also a mountain biking centre at the Olympic Park. London has lots of great cycling culture - I Bike London disco rides, London Bike and Beer Group etc
Rock climbing - there are various indoor climbing sites, often in old churches. I'll confess I don't know of an equivalent in London, simply due to the topography, but if you lived in Bristol for instance you can climb the Avon Gorge without needing a car to get there.
If you know where to look in London, there's usually something for most hobbies. There are even two horse riding schools in zone 1, for instance. I suspect, however, that most people who are as outdoorsy as you and your friends wouldn't choose to move to London in the first place.