Thanks for this. Currently living in Oxford and my experience has been similar. Have put off a move to London because I was worried that what everyone told me is true: it takes an hour to see anyone. It takes me only just over an hour to get to London from Oxford! (Though granted, there's always onward travel once there.)
Now I find people I hoped to see regularly if I moved to centralish London are moving out anyway. They are moving further away into Kent, Surrey, so on.
Basically, you need to treat London as a large region. "Moving to London" is too imprecise. It's like moving "to the North". Move to the "wrong" part of London vs your friends, and you might as well have moved to a different country. If you want to live near your friends, you need to move to the same borough, or at least along the same public transit corridors, and forget about the idea that London is one city.
Yes it takes about an hour from Oxford to London. But worse, a one-way ticket bought on the day costs something like 23 quid (US $39)! Trains in the UK are lovely, but the average price for a year of rail commuting to London is 3400 pounds (US $5770), which is absurd.
I live in Oxford and the rail costs are why I always get the bus. The "Oxford Tube" and X90 coaches run more frequently than trains, cost £18 return, have power and wifi, are comfortable, and deliver you to the centre of London in 1-1.5hrs (or assorted stop further out, plus stops from the ring-road through to the centre in Oxford). Usually less crowded and more comfortable than the train too!
Completely back this up - they also run frequently enough that a lot of the time you don't need to worry about their timetables (at peak time between both services - which are nearly identical - there are 8 or more scheduled every hour), and offer services at times when trains don't run.
Miss them very much now I've moved away from Oxford and living about the same distance away from London to the North, where trains are my only option.
"Everyone is busy" and "Too much distractions (low signal to noise ratio)" were the two main reasons I've moved away from London (and the UK) having spent 8 years there to a place where people can still enjoy slower pace, appreciate those "little things in life" and do not make the Saturday party over with the last tube train (departing slightly after midnight). (Yeah, I heard the tube will be running until 4am on weekends - it's just a shame many friends grown their families and had to relocate further with rail links. It's easier to have more quality time with them now going together on holidays rather than living in the same city).
Now I find people I hoped to see regularly if I moved to centralish London are moving out anyway. They are moving further away into Kent, Surrey, so on.