Hi, I lived in Crossthwaite Avenue for 4 years and wouldn't say it was rough at all - I always felt comfortable coming home in the dark late at night. You do get a few kids from the estate misbehaving occassionally (they used to climb onto my hedge and sometimes into my garden - did a bit of damage to the hedge but no malicious harm, letting off fireworks in teh street around bonfire night, that kind of thing) but other than that it's fine and a very handy location in that you're so close to dulwich, denmark hill and camberwell. Good luck with the house hunting!