Take the A21 at jct 5 and then about a mile later take the exit signposted for Westerham A21.
You'll cross over the M25 and be offered another right exit back onto the motorway.
Take it and you pop out on the 2nd of the 2 M25 echeloned slip roads after Jct 5 and you'll avoid all the fun and games.
I do it all the time.