Its you Ajsfwu that wakes me up early on a Sunday morning then as you exit Westerham! Lol it is a cracking route I am fortunate enough use it as a cut through on the way to work. As with most routes an early start will find you alone on the roads. Just be aware of the wildlife when you reach the B269. There is a big pheasant shoot on both sides of the road and the buggers seem to take pleasure in flying at head height straight at you. O and there are quite often deer strikes along the stretch as well but mainly at night.
Nice routes around South London are hard to come across, and this is the nearest route to me that I have found to get out onto a good road or two.
The loop indicated is quite nice and easy to get to from South London, although it is not very long. You can stop off at a cute little town called Westerham for a drink/afternoon tea, and from there you are on the A25, so can easily go to Boxhill (West) or Oakdene Cafe (East, near Brands Hatch), or head off South from here onto one of the many nice roads into Kent/Sussex.