Yes, Edward, I am into Sportives - the most recent one I did was the 110-mile Tour of Essex last month. However, I haven't done an Audax yet.
The Chase the Sun ride is in its 8th year. To increase participation, the organisers have incorporated another start-point at Richmond Park, making the ride 146-miles, for those who can't get to the Isle of Sheppey, or do the whole 205-mile route. I might have to opt for the Richmond start instead.
However, when the main objective of Chasing the Sun is to ride from sunrise on the Kent coast to sunset on the Somerset coast, I feel a bit of a cheat starting at 9am in London.