Oxford and Cambridge are quite similar, though there are some differences between the setting as Oxford is a bigger town than Cambirdge. When my friends from Cambridge have visited me at Oxford, they have commented that there seems to be more going on here, so you might want to take that into account. Also, Cambridge focuses more on module scores at AS while Oxford places more ephasis on GCSE grades and spends more time on interviews.
You would also need to look more in detail at the course once you've decided whether you'd prefer English or History because they are not the same between the universities. For example, English at Oxford requires that you do Old English in the first year of your degree while at Cambridge I think it is an option for second or third years. Both courses at either university are of course accademically rigerous and stretching and are taught throught the tutorial system.
Oxford is not scary or intimidating once you get here and all the colleges make a huge effort to make you feel at home with plenty of welfare services and people for you to talk to if you have any problems. The courses you're looking at are some of the biggest in Oxford, I believe that English and History are second and third, with only PPE having more students, so you should naturally mix with a number of people through your course.
People come from all backgrounds in Oxford, I would say that are probably more people from the south, but it doesn't lead to people from the North being left out. There are plenty of people from the North and from countries across the world and at least to me it doesn't seem that there is a 'North/South divide'.
Everyone is likely to propose their own college when you ask for nice friendly colleges :P so I will put in a shout for the lovely Exeter College, Oxford. If you're looking for someone friendly the smaller colleges (like Exeter) might suit you better than somewhere larger like New or St. Johns but being honest I wouldn't say any college is going to be unfriendly and people tend to fall in love with the college they end up at. Accommodation and food vary between the colleges. All students across the university live in their college in first year, in later years some colleges have their students live out of college in Oxford, while a few provide accomodation for all three years. Some accomodation comes with kitchens while at other colleges you have to eat communally.
Things like kayaking would be University wide generally so not something that you really need to consider when making a college choice (and societies like this are a great way to meet people from other colleges).