In reply to AJM: I lived in the area for a few years (sutton).
I'd recommend getting a monthly pass for craggy, then you have the choice to go bouldering in Sutton or leading in Guildford if you have a partner for the night. Also if you're really keen to get some routes done Guildford has a couple of auto-belays.
The Sutton wall is very good and has a reputation for being very friendly, and from Dorking it's easy to get to. The route setting is pretty good and it doesn't get too busy so you never have to queue for routes.
Stone Farm is easily doable from Dorking for an evening. I'm not sure of the quickest way from Dorking but ask Robert. The M23 handles rush hour very well and I'd be surprised if you're more than 50 minutes away.
I found the other crags to be a little too far unless it was midsummer with the longer evenings. I'd also get a nice beefy pad if you don't have one already, soloing with a pad is much more enjoyable than top roping (especially at Stone Farm as it's pretty low and has very good flat landings).