Belated comment on the A23/M23 junction: some 20 years ago I was about 100 yards from it, riding near to left curb, and a Bentley went straight into the back of me. One dazed and confused cyclist; luckily no injury, except one smashed rear wheel. As Bentleyman was ranting about me riding 'all over the road', I became aware of a motorist running back to us. "I saw just what happened - if that cyclist doesn't get all he needs for his repairs, I'm calling the Police". Good Samaritan.
If going that way on my own, I take the divided-off cycle lane (don't think it was there when I was pranged), stop as the M23 starts and walk over when there's a gap. But I feel quite safe in a clubrun bunch.